Bought the Tekonsha P3, works great, thanks for the suggestion. I set it to "B1" boost, since regen doesn't activate the trailer brakes, so if I hit the brakes in the car I don't want it to "start at 0" (default/no boost), although I assume with regen it would not really "start at zero". B1 feels pretty good (starts at 13%). I noticed the controller will lock the tires at ~8V if the brakes are cold or have sit for 24+ hours, but after driving for a bit (just a few braking events for testing) they don't lock up (gravel road) even at 12V ... so I set to 10V ... need to research this a bit. I'm testing by slowly driving (5mph) after hooking up then manually engaging the controller until I hear locking (haven't heard traction control kick in, which makes sense given the vehicle is 5712lbs).
The other thing I noticed is my Model Y LR AWD (with I assume single casting) shows a payload capacity of 1100 lbs and change on the sticker, which is higher than what some other LR AWD posts state (~800 lbs) ... so I wonder if that has been increased with 2021 models (7 seater).
I'm currently using a 0" rise multi-ball. The trailer comes with a sway bar attachment so I'm trying to find a way to get a 3/4" rise w/ a rocker cushion ball (2-5/16" w/ built in 1-5/8" rise for the cusion) w/ sway ball mount (3/8" thick rise) that is level w/ the ball. So far I have not found a way to make that work. (I would need to find a way to get a 1-1/4" ball mount drop to make up for the rocker/cushion and sway adapter rise).
Thanks for your help and suggestions.
I did end up buying this trailer but does sit too high as it is for "offroading" and has 28.5" diameter mud rover tires. I'm looking to drop from the 15" to 14" rims and smaller road tires (we will not be offroading) while staying within specs of the original trailer tires.
David