Have a look at some of the builds by cryoscum. He held the Tripoli O class commercial record for altitude and speed. O3400 to 66k' and M3.6 IIRC
Here are a couple of his threads on the Australia forum:
https://forum.ausrocketry.com/viewtopic.php?f=10&t=4666https://forum.ausrocketry.com/viewtopic.php?f=10&t=4253https://forum.ausrocketry.com/viewtopic.php?f=10&t=3659
There should be some useful information there .
Enjoy the build!
His engineering and fabrication solutions are incredible!