I was thinking of building up my old Cotic Soul frame (medium) in a road/cross type guise for my 10 year old son with rigid forks and may be drop bars. Kinda inspired by a mate with a Surly Troll who’s lovin’ it.

Ever heard of, seen any pics or have any comments/suggestions on such a wheeze?

I did it with a Cannondale Bad Boy commuter. It needed a 50mm stem to keep the reach reasonable as the top tube on Mtb’s is much longer than on road cross bikes. An old school retro MTB frame would likely be more suitable but if you want a disc back end you’ll probably find the top tube too long anyway.

Unless your son is very tall, he may struggle with the reach to the hoods

Unless your son is very tall, he may struggle with the reach to the hoods

Exactly what I was thinking, at 10 he would probably need an XS or S depending on how tall he is (obviously 😉 )