Well ill put in a little update since i feel the need to backup my thread
. The seats are holding up just fine and imho :p are very strong and safe. I used 1/8 inch think, 1-1/2 inch wide sold hi-temp, hi grade, steel for the bracket. The rails/sliders are all part of the celica seats. Everything is bolted together with 3/8" or bigger, grade 8 or factory bolts.
Just because its not oem dosn't mean its going to fail. Ive actually had real sparco brackets before (cost me way to much btw) and imo were garbage. If anything those would brake in-two without even thinking twice about it. To each his own i guess.