Two things show up here, vern.
First - Planning and double checking can save a lot of "fix up" situations.
Second - It is far more cost effective to spend a few dollars more and get a larger quantity. Purchase ,say, six sets of Corby bolts from a major supplier(Jantz,Sheffield, TKS, Pop's, K&G,etc) and the shipping is the same. It is spread over a larger number, so it is lower per unit. Also the price is often cheaper in multiple quantities.
I was grinning when reading your post. It brought back memories of myself as a small boy, planning a small project, and counting exactly what size nails and how many I would need. I would walk to Hobbs Hardware and ask Mrs. Hobbs for "three #6d finishing nails, 1 #16d common nail, ten #10d common,......untill I had everything I needed. She would always drop extra nails in the bag, knowing that I would loose/bend/need one more . She would carefully weigh the bag on the scale (which probably didn't even weigh that low) and tell me that nails were $0.55 a pound and mine came up to 1/10 pound. She would usually finish with something like,"Call it a nickle even, since you are a good customer."...............I really miss business people like that. The big box stores are nice, but you have to remember that they drove all the Mrs. Hobbs' out of business.
Stacy