inch to metric (bolts and nuts)???

Is there anymone that have used metric bolts and nuts? Or is it a must to use inch bolts?

I believe both are listed on the parts page.

I have made the 25.4 version with all metric fittings.

There is no problem with 8mm bolts, as near as dam it 5/16 (7.9375) the problem is with the nuts for 4mm, 7mm across the flats is the standard, I am lucky in having a small machine shop, made my own nuts out of 5/16" stainless steel hex bar.