Stuart Watts

(New IOM owner here). I have an old Fat Boy IOM which needed some fibreglass repairs which are now complete. I have an A rig only with a groovy mast. Sails are not special and need replacing but I am looking to get on the water with what I have at the moment before I decide on a new rig/sail. Some of the rig set up is new to me (shrouds and mast ram!) but I have some knowledge of mast rake/boom angles/twist etc so set up will not be completely unknown to me. What I am struggling with is mast rake. The foredeck is angled and thereafter is reasonably flat/level? My query is how much rake is a good start? 0 to 1 degree ish?? and without knowing if the deck is level/flat to the waterline how do I measure the rake degree? I suspect you might say I need to identify the waterline and check that against the deck, but is there another way? Many thanks for your considered help!