thanks everyone for your valuable input! i think we're going to try out drew's answer here. as i get older, my brain doesn't handle all the math as well as it used to but once i get a spreadsheet set up i won't have to do it again!
answers to the various questions:
i use synthetic Bar Tops. they are the correct size, but it seems with slight variation in glass and corks, some fit perfectly, some are a little tight, some are looser. we seal them with a self-adhesive strip over the top of the cork and down the neck. it's a bit more work, but looks sharp. i'm sure they don't hold as strongly as a shrink capsule would, but until i get a really nice looking capsule, i'm sticking with the extra work!
good luck all, and many thanks,
rifino