just curious to see what does and doesn't matter to people when they build. there are specific rules that govern rollcage / chassis construction. they are not available in your local drag racing spec. you can go to the rule book to see what spec your chassis needs to be but, after that you need an SFI manual to determine tubing placement and diameters. for instance:
pro stock requires SFI spec 25.1e
pro mod requires SFI spec 25.1e or 25.2
top sportsman (if quicker than 7.49 sec.) requires SFI spec 25.1e or 25.2 or 25.3
(if 7.50 or slower) requires SFI spec 25.1e or 25.2 or 25.3 or 25.4 or 25.5
i have read the 25.2 manual and i'll give you a for instance. there are 4 different rollcage configurations that are approved for 25.2. they range from the driver helmet being in front of the main hoop to the drivers head being behind the main hoop. the location of the drivers head (so to speak) denotes the locations of the rest of the tubing. same with the floor tubing options, dash /lower windsheild bar and gussets, and the cross tubing in the halo bar. how the flooring sheetmetal is attached is also spec'd. so, questions like Tom's about a pro mod / pro sportsman ( i'm guessing he really means top sportsman) chassis flooring aren't always cut and dried answers. the two could be the same or they could be different.
any way. for those of you to whom it matters. there are rules that govern what, where, and how tubing should be placed. i'll post some pics of the rollcage differences when i can.