Teardrop sides construction

I am new to this forum and starting restoration of 52 kitt on 9/7/09. All wood dry rot. Need to change out. Sides are a little less than 1/2". Old wood is not up to current measuring of plywood. The 1/2" I bought shows 1/16 less that the old wood. Should I expect any problems with re-attaching the roof aluminum? Maybe screws wont go in on the new plywood??? Any help?