Thank you all for the warm welcome and for all your help!!
I added 1.5 cm on all sides, and it 'appears' to be working. I have all the pieces on my 'test' quilt cut, and started to sew 'em together, but decided to call it a night for now!! Hopefully I'll get the rest of the top assembled tomorrow, and I'll feel comfortable enough to start on the one for my friend!! I just don't want to make mis-cuts on hers--no way to get more fabric if I do!!