RE: New plane is here!! Question on engine cover?
You should never build a plane such that it can't be serviced. The cowl should absolutely be removable.
If it doesn't slip over the nose of the fuse and there's nothing to screw it to, glue some hardwood or ply blocks to the firewall. Set the blocks back from the edge by the thickness of the cowl. Tape the cowl in place and drill through the cowl and block to give accurate screw pilot holes. Then enlarge the holes in the cowl to the screw clearance size (screw drops into hole but stops at head).
What's even better than screwing into just the wood is to drill through both cowl and block with the clearance size bit. Then drill the blocks out larger so you can glue in pieces of yellow nyrod. The screws going into the nyrod will not rattle loose and the holes won't wear out. I also like to use a nylon washer on the screw to protect the cowl.
Dave