Mast rake

[noscreenname]

I race a Columbia Sabre. She's a 7/8 rig with straight spreaders and all shrouds parallel to the base of the mast (deck stepped). I am trying to find out how much rake to induce in the mast for our conditions 5-15 most of the time. I hired a local rigger to give me advice and he said 12" or more. This seems a bit extreme to me. Does anyone have a suggestion?
General specs:
LOA 32
max beam 6'4"
4500