I agree the crouch belt is only to maintain lap belt position and frankly with also wearing the stock belts using the frame of seat on a C4 is OK, for if its strong enough to hold a 300 pound guy it can just as well support the crouch belt.
For the C5 I have AS&M system and you get a metal plate that uses both front frame bolts to floor support mounts and has a hole in the middle to bolt the belt bracket.
Originally posted by Dreamin:
I have the same question... what is the best way to mount the sub-belt, with stock C5 seats in place? Down the front of the seat and back to a rear seat bolt? What about down the front to a front seat bolt?
It is my understanding that the sub-belt is primarily there to hold the lap belt down (in place), so it does not lift up over the hip (pelvic) bone in a collision. It's the lap belt holding you in place, not the sub belt (sub-belt holds the lap belt in place). This means (1) there is not that much force exerted on the sub-belt, and (2) sub-belt can be mounted almost anywhere, as long as it is pulling really tightly down on the lap belt.