Most of it is prefabricated, then modified to suit. With cost of steel and time, in most cases it is more cost effective to buy something close and tweak it. I was able to clock my axle when welding in all the new stuff so that I achieve perfect pinion angle and have the adjustability and axle sitting where I want. I use a lot of Artec builders parts. They seem to always have something close to what I want, fast shipping, good pricing and great product.
But since you like math IC is about at the center of the engine, anti squat is between 80-85%. Have some room to play with these after I shake it down. Only really driven it on the street currently. It does drive on road well, corners well, and seems to have good control on rough roads.
Also I plan on going to 40s soon and I am trying to keep the stress off the axle and brackets, hence a great deal of separation. Ideally I was shooting for 10-12 inches of separation on the axle (25% of tire size) but had to make a bit of adjustment due to frame side upper mount location.
The lower IC being where it is should give you nice stable handling. That's where I set mine and it works very well. I set my separation at 10 inches even though I'll probably never see 40's. Yeah upper link setup is a pita, no doubt about that. I just said screw it and made a crossmember for the frame links. Got a nice double triangulation that way. Are you getting much lift in the rear with that anti squat?
Yeah, I wondered how the weight would affect rear lift. Your A arm mount is adjustable so you should have a fair amount of adjustment on the AS. I've been running my AS at about 60 percent. Gives me nice neutral behavior. Probably will only go higher than that if I were to spend time in Moab or some such place. 80 percent would be preferable if I were doing a lot of steep climbs but overall I like the neutral handling.