my house originally had two 8' garage doors with a 1' center post, but i would like to put in a single 17' door instead. about 20 years ago the garage was enclosed and they took out the center post and put 2x4 framing in with a sliding door on each side and regular plywood siding in the middle where the post was. no modifications were made to the header or original framing. it has has two 2x12's side by side across the full 17 1/2' span that are sitting on 2 vertical 2x4's on each side. it's a single story gable roof and the rafters run front to back, built in '59. would this hold up? i REALLY hate double garage doors, and i know 16' doors are common, so i wouldn't think another foot would hurt. i can't see any sagging in the roof or 2x12's and i don't think the sliding doors/siding are holding much weight if any at all. just thought i'd ask the pros before i go tearing stuff up. i'll get a pic later on tonight if i can find my camera.