I redesigned the cowl mount because the stock one is inadequate. After a few flights I was always chasing tightening screws and in two cases the cowl got loose in flight and rubbed the back of the prop. So out with the stock set up and in with the redesign.
I'll self edit my previous suggestion and say use lead shot in the cowl ONLY if you mod the cowl mount.
Ive posted my work on this before but if your interested I can find my post and link it.
I split the cowl from the cowl flaps and made the cowl ring stand off 0.75 inch forward of the firewall. The taper of the cowl requires the ring to be resized slightly. The cowl ends up in the same location relative to the fuse but now the cowl has button head screws radially installed into the wood ring.
The cool part is the screws look good enough, minimally noticeable, and access is easier. I would suggest making a copy of the cowl ring in a proper marine plywood because the supplied wood is crap and delaminates with a stare! Lol