I do the S2 7.9 mast myself, different animal of course...
The mast step on the 7.9 is a single pivot pin, and half moon mast base (to provide a smooth pivot)... also the mast is lighter on the 7.9 I think.
But that being said, your observations on needing 6:1 are spot on.
I also use an A-frame... and the spin ring to raise the mast. So its only like 4 feet off the mast deck, pulling from 8 feet off the foredeck.
Anyway, I think the ginpole is better for torque, as I've mangled 2 5/16" eye bolts at the top of my A-frame, I've moved up to 1/2" eyebolt, and have reinforced the A-frame due to the stress on it. But I can still get the mast up even with only the 4:1, but like you said its tough... I thought I'd maybe throw another block at the setup, and make it 8:1.
The 7.9 is a single lower, swept rig fractional, but my prior boat, a Capri 25 is a dual lower masthead, and I can confirm the length of the lowers are different on that design as well.