Charlie,
I've reconstructed a old broken mast and added some uni to it with the thought that I'd use it for when I add a spin to the Acat.

I wouldnt risk my primary mast, find an older mast, and add some uni to it to stiffen it up.

And dont go more than 1/3 the distance between the hounds and the top of the mast with the hoist on the kite. And keep the main sheeted when you are flying the kite.

Bill