Are you building this 5.2 to sail single handed with the chute?

You probably have enough power in the main so you might want to add the chute like the F18HT or the Marstom M20 or CFR 20 or like the F16's/F17's going uni.

This allows you to split the forestays into two and put your pole anywhere you want in the fore triangle. The bridal foil is designed to deal with the increased loads induced when you oversize the jib and so you lower it's tack point. I don't think it is a great way to go.

I would bet that the 5.2 failures were caused by a lack of attention to the front beam, dolphin striker and how it seats in the hulls. If I remember, they use the steel straps and alu beams and after 30 years... this was probably not a happy marriage!

At any rate...This game is all about luff length of the spin.

The shorter the spin luff.. the higher the pole can be... the smaller the squeeze on the bow.... and the slower the spin is...

But.. you rake the mast aft as far as you can... (bitch to get under boom)... you are limited by the mast base (able to still rotate) and your ability to rake the rudders under the boat. This gives you max upwind performance. You want the rig to be balanced.

Pick a safe height on the mast for the hoist height bale/line limiter.
(max half way from hounds to tip... safe = 1/3 way hounds to tip. If you use a 10 - 12 foot pole... you can find that alu extrusion lots of places. Use an F16 spin and you are good to go.

You should be able to get the proper tension on the spin luff and have enough prebend in the pole induced by the pole front stays.

When you use the foil... you are setting max height of the pole in the middle of the pole by the length of the bridle foil wires. Now you have to induce some prebend in the pole by tensioning the stays from the bow tips to the pole tip. This will really tow in your bows... or you need to build a pole strut to induce the needed prebend and just use the pole stays to keep the tip centered and in column.

Have fun
Mark