Engine will be a YS 110...mounted on it's side with a Pitts slimline muffler...
Can you say "LIGHTNING FAST VF EDGE-540" ? Man it's going to scream !!
The firewall is very strong. But as ckangaroo70 suggested ,,, beef up for the power. To save weight I'd just go for the tri-stock and some 30-min epoxy. The cloth makes it heavy.
Don't forget to seal the surface gaps and add the extra hinge to the ailerons. It's a fast plane for an Edge540.