Is it legal to remove the steel angle that is bolted behind the front seats of the '97 Civic. If it is it will be removed and replaced with a low horizontal tube in the main hoop.
Do you have a pic? Is it a part of the seat mounting? If it's just something that the seat mounts to I think you would probably be ok removing it. If it's a part of the unibody, then I'd say no.
as long as:
1.) it is to facilitate the installation of safety equipment (roll cage etc)
2.) If it is part of the roll cage you are allowed 8 points of attachment.