I have a Pat Tritle designed Dumas DH89 Rapide to build along with a SIG Dornier Do-217 and wasn't in love with the conical nut of the prop adapters. I had cowlings made by Marc at Rabid Models. While he was at it I have a Top Flite GE P-39 Aircobra I think I may go electric and he made the perfect 3.5" spinner to fit! I love the cannon in the center of the spinner. the P-39 Aircobra sported a 37mm cannon mounted thru the spinner. The The DH-89 spinners are only 7/8" in diameter and as you can see the the Dornier spinners fit the cowls perfect!