The centering rings were reinforced with balsa strips

This being the largest diameter rocket I have built so far, the cardboard centering rings seemed to be a bit too flexible.  I've had smaller cardboard centering rings fail, so I reinforced both rings with balsa strips liberally glued all over.  I am hoping that this can withstand the heavier thrust of E and F motors, if I decide to fly that high.

The metal spring clip for the motor was not supplied by the kit maker DynaStar.  I added it because working with masking tape is a real pain.