MichaelK hi ya there
If you do a search on this Forum for HMS York type 42 build, you will find it somewhere in Warships - and you will see how I have made a ply-wood jig up. This holds the 2 prop tubes and shafts in line, whilst I tack the tubes in place & then glue with epoxy.
I normally , like Shipmates60 has suggested, cut slots for where the 'P' frames or 'A' brackets locate in the hull - slide them in place over the shafts and then tack them into position using superglue.
Ensuring that the shafts turn freely. I then mask off with electrician's tape around the base of the 'A' frame where it goes through the hull ; I next turn the hull over and I make plywood packing pieces which slip over the 'A' frame leg where it comes through the inner of the hull - this is then epoxied to the hull bottom along with the support bracket leg of the 'A' frame. The packing piece ensures that the stress is spread out evenly on the bottom of the hull. If this is difficult to follow, just give a shout and I will put a sketch on here for you.
aye
john e
bluebird