could i run a one piece prop. whats the pros and cons

depends if there is room and how speed limited you want to be.

critical speed.

i suppose the length of it would be the first problem. im having mine rebuilt by chard props of bristol having it balanced at the same time got bit of vibration going on hopefully this is it. they recon the splines on the front sleves are slighty twisted the centre bearing that i put on from flea bay isnt the best they found play in the joints i couldnt infact the front sleve is the wrong one so hopefully it should be smooth as