As long as you've still got sufficient room for the recovery system, the longer motors should be no problem. There's plenty of support in 14" of motor mount tubing. Heck, longer motors help move the CG forward, too. (unless you're talking hybrid)

Fly it on both! Cessaroni for a good reliable cert flight, then hit it with a J570!
Just my $0.02
Ken

Use a J825R 😆

Honestly though, as Ken said, the motor tube length is largely irrelevant to the length of the motor you can use. Go right ahead and pick whatever motor you want to use. It should work fine regardless.

Thanks for the info.
I have plenty of room for longer cases.
My thinking was that the ejection charge would be better to occur in the motor tube than the body tube. I will use plenty of dog barf to protect
the shock cord below the piston,which I normaly do anyway.
Too, will be looking for Nar members to Cert L2 this Saturday.

DenB

You shouldn't have a hard time with that.

Your thinking was correct on the longer motors though - use plenty of dog barf, and just don't overdo it on the charge (which is good advice regardless with a piston). I've had excellent luck with ~0.8-1.0 grams in a 3" tube, and 1.3ish in a 4 inch, though on some of my larger 4" rockets, even with a piston, I go with 2g to be sure.

That is why I prefer the AT motor reloads over CTI for piston rockets.
The CTI's have very powerfull ejection charges, sometimes too much
for small Dia. piston rockets. I have learned to mount the piston upside down from the instructions.
Thanks again for the advice.

DenB