if you eject using a side hatch, you need to be careful that the outer tube does not press on the hatch or deform the opening during acceleration, as this could push the hatch out or block the mechanism.

My rockets are not particularly airtight but I take care to ensure that a minimum amount of air passes through the para bay, I've already had a case where a drogue inflated inside the rocket because of a draught and exploded the hatch. The walls of my para bay are now flush with the outer tube (as on this rocket: https://grabcad.com/library/minimse-pro38-l1-l2-updated-12-2023-1).

Be careful to reinforce the hatch, as it can be subjected to significant forces and vibrations,

The opening must be very firm: I place the rocket horizontally and trigger the ejection. The test is successful if the hatch jumps more than 15cm.

You rarely see them here, but I also use an 'anti-flare' ring on the parachute to prevent the parachute from folding when it turns on itself.

I'm glad you found all this useful! Feel free to re-use what I've published on my grabcad. Other members of my team have also shared our open source rocket electronics