Just made this and I thought I'd share it since it may be useful to others:
The numbers in the table are the percentage size of the donor part relative to the finished model scale, so for instance, if you're building a 1/72nd model and you want to use a 1/48th part, go along the "72" row until you get to the "48" column and it tells you that that part is going to be 150% of it's original size in 1/72nd.
I can't post it as a spreadsheet but I'll send it to anyone who wants one. I could also extend it to cover other scale combinations. let me know if you want either.
