Seat mod...Nylon spacers okay?

Just make them from aluminum like I do. You can buy bar stock for around $1-$2 an inch drill 3/8 hole, I just machine them so they are close to precise thickness and debur all edges, which anybody can do with a small amount of time. I do recommend to be at least as close to the same width as that frame foot which I use 1 1/2" wide stock. I just don't think $10 each was much for the aluminum ones. But it is probably one of the best feeling mod around. You can find short pieces of bar stock on Ebay. Good luck

 

Being that humans vary greatly in size, and the Tacoma is rated as safe for 5 foot tall 250lb people, and 6 1/2 foot tall 105 lb people, and all body types and shapes between, a 1” rise in the back is unlikely to change crash dynamics as much as basic human physiological differences.