Windmill Class Association

I am looking to purchase an older wooden windmill, but have some question as to whether the aluminum mast is the right length...can someone let me know what the appropriate lengths are for a keel mounted and a thwart mounted mast? (I am not sure which is included). I intend to join the association when I take ownership, determine hull number, etc. in the next few days. I just want to be sure someone hasn't substituted a mast from another class.