Here is an idea that was suggested to me by an "old Salt" but I haven't tried it .....yet. It makes some sense since I too, have the type of mast that requires a 90 degree turn.
He thought I should rivet another tang on the side of the mast (so that the pull would naturally turn the mast 90 degrees) and abandon the forestay as what I attach to the winch. I haven't done it yet because I don't want to drill more holes in the mast # 1 and # 2 I haven't figured out how I would attach a line to the tang that didn't have to be left in place while I was sailing.
For holding the mast in place at 90 degrees I just fabricated a PVC pole with a "V" on top and bottom that rests on the ground but holds the mast on its side 6 feet off the ground behind the rear beam. I use the pole to help lift the mast while my helper cranks the winch. With the 6 foot pole I can lift it high enough without having to climb onto the tramp.

Let me know if you can think of another/better way. I'm all ears.

Greg