The DA 50 ships with 2.75" long standoffs that maintain the carb ahead of the firewall if you use them without spacers about 1/4". As such there is NO need for a hole in the firewall when using this engine. The problem is that the WH Edge needs the engine 3/4" further forward to mount up correctly. I simply used some some spruce stock purchased at the LHS that measured 3/4 x 3/8, laminate two peices together to create 2 blocks 3/4" square, mount the blocks to either side of the firewall and drill through to allow passage of the engine mounting bolts.

Simple, light and easy. Be sure to coat the whole firewall and all exposed wood under the cowl as gassers will spit oil out of the carb and oil down the wood, fuel proofing is a must.