Sierra has prop hub extensions for the DA50 and DL50.
http://www.sierraprecision.com/prod32.html
I use a slimline pitts muffler on mine. A buddy uses the J-tec muffler on his. Says he wishes he got the slimline instead. Dont remember why. He still uses the J-tec. My slimline fits real good inside the cowl of my GP Yak54.
Edwin