If you put the motor
where the batteries
are now - where will the batteries
go? They weigh far more than the motor
so moving them forward will push the CoG even further forward😲
Re shaft angle; as flat as you can get it for the size of prop you want to use.
This is to reduce the forward rotation
moment of the thrust which tends to push the bow down. The further back you fit the motor
the larger the angle will inevitably become due to the space needed for the motor
BTW: Why two NiMh batteries
I would be tempted to change the set up to a brushless and a single LiPo.
This will significantly reduce the total weight as well👍
You did say the boat is 'a heavy model'! 😉