If you had any means to control the SHAPE of your windsurfer sail, you wouldnt need to 'lean it'.
Pre-bending a mast is STANDARD set-up and your mainsail was most probably cut expecting this prebend in the design.
Suggest also that you go to ArvelGentry.com
---> magazine articles and start at "Checking Trim on the Wind" (and the next sequence of 3 allied articles) ... as sail 'shaping' is equally as important as sail trim. Probably 95% of all non-racing sailors have no idea of 'sail shaping' .... and have 'problems' with 'weather helm', etc. etc. etc. etc.