Jayco Flight SLX 7 ball size and height

It is surpisingly difficult to find information online about the ball size and height for the Jayco Flight 7' wide trailer series. The manual from Jayco is absurdly general, and while ball size and height are specified on Jayco's website for some trailer years it wasn't specified for 2020 models for some reason. Basically most answers involve looking at the tag on the tounge of the trailer to find out, but since I can't do that yet until I pick up the trailer the other option calling the company to find out (although some people have reported not getting a good answer from doing that either). It also doesn't help that most people online are looking for info about the Jayco 8' wide trailers, which seem like they may have a different ball size. It appears as though there are only three standard ball sizes, 1-7/8", 2", and 2-5/8". It looks like the 8' trailers use the 2-5/8" ball, while the 7' trailers may use the 2" ball.

This expert at e-trailer points out that convertable balls are a purchasable product that can be made to do any of the sizes: https://www.etrailer.com/question-335215.html

This is a question from somebody who has an SLX 195 which is probably a 8' trailer. However his question includes the tidbit that his coupler height is 18.5" which I think I've seen elsewhere. That's a pretty high height considering that my hitch height is 11" for the Sienna! The answer to this question is notable because it contains links to info about all kinds of other things that I've never heard of before, like a trailer weight tester and a weight distribution shank. https://www.etrailer.com/question-523734.html

Here's my 174BH on a different website that at least has the courtesy to specify the ball size. This has it at 2". Also this page has the best pictures I've ever encountered of this model: https://rv.ruckify.com/2019-JAYCO-JAYFLIGHT-SLX-174BH/

2008 Toyota Sienna 7-way trailer harness installation

This video by UHaul showed that off-the-shelf trailer harnesses are sold that have connectors that plug right into a Sienna's existing wiring harness. This would be tons better than doing wire splicing myself:

https://m.youtube.com/watch?v=hvLO-HiYEFE

However, a lot of searching revealed that these harnesses are always to 4-wire harnesses ("flat 4"). I've come to the conclusion that this is because there's no easy way to standardize picking up the power wire for the 7-way connector from the battery, the reverse lights are a huge challenge because they're on the hatch but most trailers you'd hook to a Sienna wouldn't have reverse lights anyhow, and the brake controller is something someone would nearly always have to customize. Consequently, most people posting to forums seem to get the 4-wire harness then get a 4-to-7 wire adapter. Here is the best 4-to-7 system that I've found so far. It has the 3 extra wires stubbed out to butt connectors. It has a nice mounting bracket included. And it's sold in a kit together with a nice 4 wire harness so you know they'll mate together. The instruction sheets are weak but they're available to preview online.

https://www.trailerjacks.com/04-10-Toyota-Sienna-7-Way-RV-Trailer-Wiring-Plug-Prong-Pin-Brake-Control-Ready?language=en¤cy=USD&gclid=CjwKCAjw_o-HBhAsEiwANqYhp0Z0Ly6E_2Hr6V48Nw3tpYa0hWnhopVr6NGZGdlcDHb2Tck6CgJcnhoC8J8QAvD_BwE

Next here are some links to forum posts of people trying to solve this same problem, some of which contain people giving out quite useful info such as specific part numbers for the 12V relay or a brake controller from Curt:

Near the bottom this has a post with some good part numbers: https://www.siennachat.com/threads/7-pin-wiring-ques.1897/

Here's the forum thread answered by madman "Brian" where he cut and spliced two controllers together or something and otherwise did his own wiring. The thread degenerates into a discussion of stranded wire current carrying capacity, so I really should try to read every word in this one even if I was looking for a less labor intensive solution: https://www.siennachat.com/threads/7-pin-wiring-harness-for-2006-sienna.1030/

This thread starts off on fire with a guy giving his entire parts list for his 7-wire install (2012 Sienna though). This thread may have all of the info I need: https://www.etrailer.com/question-83028.html

So, which 4-pole adapter harness is the best? There are a lot of brands out there, including Curt, T-One, and Hopkins.

Here is the Curt harness. Their ad copy makes it sound quite inspired: https://www.etrailer.com/Custom-Fit-Vehicle-Wiring/Toyota/Sienna/2008/C55580.html?VehicleID=20081176415

2008 Toyota Sienna Tow Hitch

The class 3 hitch that John gave me mounts to a vehicle's frame through three holes on each side. The Sienna has three holes in the frame on each side. However it appears as though nearly every other dimension of the hitch will be mismatched, as hitches are not standardized and will be different for every vehicle. It is fairly easy to find vehicle specific hitches however, and they are relatively cheap ($150-$200). The major manufacturers presently for hitches which fit my Sienna are Curt and Draw-Tite. This link is the money hit for chosing between them (oddly the Draw-tite wins on tounge weight and other specs by a lot):

https://www.etrailer.com/question-35975.html

It turns out that YouTube has tons of videos about how to install hitches on Siennas. What I learned is that if I had the plastic underbody cover the job would be twice as long, but since I don't have that then the weld nuts on my frame are essentially destroyed by corrosion and I'm going to have to spend a lot of time chasing their threads. Crazily the UHaul installation videos beat every other one out there hands down.

Here is one of many videos showing how agonizing doing the installation is with the plastic underside cover: https://m.youtube.com/watch?v=GTk8iqXha7Q

Here is the Uhaul vide for installing the Curt hitch: https://m.youtube.com/watch?v=cDU9Wo_MDGY&t=20s

Here is the UHaul installation of the Traw-Tite. The tool list shows the bushing pusher pliers that I will totally want to pop the tailpipe hanger off on the passenger's side: https://m.youtube.com/watch?v=Guz3s1FW7hA&t=18s