100 guys will build and have adequate material and 3 come up short as they didn't plan ahead. The beauty of this Legal Eagle group is we have such diversity of experience, guys that have build several planes and folks that have never built a birdhouse.
HOWEVER we are not above making a mistake and will quickly address any reported shortages hope this helps
I as well, have laid out many fuselage sets, and as far as I am concerned, the #1 rule is to cut all of your longest tubes first, working your way down to your shortest tubes. For the simple reason you can't make your short tubes longer but can always shorten your left overs to fit the shortest lengths needed. (if that makes sense)
Simple case in point, if you need two 12's for longerons, and have the two 8's left, and need parts times 2 that equal up to the two 8' pieces, you would have almost zero left over.. But if you took 3- 5'ers out of a 20' length, then you have one 5' piece to work with, with far fewer options.
It all comes down to planning. It might seem odd at first taking out the longest pieces from the 20' length leaving many random lengths, but it works. If you really want to get this figured out before one cut is made, use a spread sheet, and you will quickly see what needs to be cut first and why.
