The trick with this (as with most boat settings) is you need an "index". Mark your tramp at the pointing towards the shroud location. This becomes your upwind default that you will return to for upwind work. Having a mark also allows you to say things like "1 inch behind the mark" instead of pull it on a bit. At the end of each race return the mast the the setting you have been using on the way to the beach and when you get in measure and record the setting in a note book along with wind observations and how you thought you went boat speed wise upwind. You'll very quickly learn where it needs to be.

If your ringer is worth half of what you're not paying him, he/she will automatically tune the rotation anyway, its part of their job.