Yes you will fit under Potter Bridge - we have done it several times in Thrift. We found it is quite easy at 6ft on the height gauge - we had 3 inches to spare according to our log. It does take a bit of nerve though - it really doesn't look as if it will go and the first time we went through against the tide so that we could back out if we needed to. In fact it works well.
We do have a special mast crutch that we use for places like the broads. It fits against the inside of the transom and once in place we leave it there. It spans the tiller and so doesn't interfere with the steering.
I will try to take pictures of it this weekend and post them on the forum. Once the mast is in the crutch it is virtually horizontal.
I can't remember how far up towards Hickling the course takes you but we found we needed to raise the keel to get up Heigham Sound.