Did you use 10' EMT lengths. I measured the distance form the stansions to the pulit and it looks like 10' will be just right.
I'm making one also to replace my Ginpole. Although the ginpole is longer and gives more leverage, the A frame is more stable.
I also got an idea from Utube to make anothe A frame from the deck hand rails to the mast slot to support the mast laterally. I'll see if i can find the clip and post it. It looks simple and secure.
Rehoboth Bay/Indian River, DE
S/Y KJ, Helms 25