Just like with my Spitfire MK XIV I used Meshmixer to slice a portion of the long nose off just in front of the motor mount. This allows me to mount the bigger motors used for combat flying and still be able to glue the tip back on over it to keep a more scale appearance. In the case of the P-51 it had an added benefit…I was able to print the tip if the nose piece upside down so that it could get better support. Usually part of it prints over air and pretty much fails…this way the part that fails prints first and the rest of the cooling duct is able to be printed with supports. Also I can double wall the nose ring area making it stronger. This came out pretty darn good.
I ran into a bit of an issue…the indentations for the screws that hold the motor mount in place are too far forward on this plane with the long nose. As a result the larger diameter motors can’t sit flush against the motor mount block. I’m going to try adding some 2-3mm spacers between the motor mount and the motor. That should move the motor far enough away to get the correct angle from the motor mount block. I’m just hoping it isn’t too far away though otherwise getting the spinner to fit properly will be a problem.