since most frane repair patches need custom tayloring to fit correctly, get some heavy poster board. make your templates for the area being repaired. this is a very easy thing to do; it only takes a little time. make sure the crusty area[s] are trimmed to solid material. you can then use your templates to cut fresh 12-14ga. steel patches for a fraction of the cost of "patch panels", even if you have to pay the steel supplier to cut'em for you. and they WILL FIT BETTER ! weld 'em in-job done !