Rudeboy, a 1/4-20 nylon bolt will have about 150 pounds tensile strength and 200 pound shear strength. On most of our planes, a 10-32 is more then ample (125 pounds tensile/150 pounds shear) and you could probably get by nicely with 8-32 (85 pounds tensile/ 40 pounds shear). I use at most 10-32 on all my big birds and have never had a failure yet. The figures quoted above are from test Weckesser Company made on type 6/6 nylon bolts. A good source for nylon bolts is MicroFastners, you can find them on the web.