Good Morning, Yoricko
Double ditto to what David William White says about precision and consistency in making contact sheets.
Re extra frames for 35mm: Over time, I think you'll find that it isn't worth the bother. Processing reels generally won't accept more than a couple of extra frames, and, as you note in the original question, the "extras" are just a nuisance when doing the contact sheets. 35 frames (seven strips of 5) will easily fit on 8 x 10 paper.