Dave:
You can see from these re-plumbing shots I took last fall whoever installed the DA-50's in mine carved out some of the bottom firewall to give room for what I think is a standard DA Pitts-style muffler
It works well comes apart easily when needed
Plane flies very well at 50+ lbs on these engines: not a screamer but you don't want it to be
Jeff's flies very nicely on G-62's with similar 3 B props: about the same power