Rig Balance
The bigger sail did mean that the centreboard had to be located well towards the back of the boat - lots of people said this wouldn't work - to the point that I started to doubt myself! But if it all went "pear shaped" I could always rip it out and move it to a more sensible position - it is just more woodwork. In the end there was no problem - centreboards can go a long way back.
I also hedged the risk of the rig being unbalanced by setting up the mast so it could be raked (tilted back and forward) to move the centre of the sail back if required. This would also give us the ability to trial different sailing rigs.