I have a DL50 with a stock muffler in mine and it was tail heavy - even used heavy batteries - 2500 4.8 v ign by the firewall, and 4500 6 volt front of fuse. Mine does have a virtual cockpit with a pilot that weighs almost 6 oz ( i know ...too heavy) so I used 4" stand offs to keep me from adding any more weight and the prop distance from the cowl is fine. The plane weighs 18 lbs 2 oz and flies great