I use a different number and size nylon bolt depending on the model. My Extra300 for example came with 3 steel 6-32 bolts into steel blind nuts. Fate caught up with it in it's second or third year and that steel and the carbon fiber gear tore the belly out. Now it has 3 nylon 10-24 nylons into the plywood. I did that back in 2010 during it's first year. A week or so ago it hit a hole in the runway at touchdown and stripped the gear off. One hole in the covering and 3 new bolts. The new patch was over the previous patch from 6 years ago.

CA after threading works too.

The Extra is a 7lb model. I've got a couple of heavier ones with 1/4-20s used with 10-24s. Lot's of flexibility by mixing. The heaviest has split mains. A left and a right gear with two bolts each. I put the 1/4-20 inboard and the 10-24 outboard on each. The 1/4-20 deals with the lever effect every touchdown. It there is a twisting stress or impact on a wheel, the 10-24 provides a release if needed.

With metal or CF gear, using steel bolts pretty much guarantees something is going to be destroyed.