G'day guys i have just started doing some sup foil downwinders ( paddle assisted) on an axis set up. For dinging and windfoiling i use the 900 mast and for surfing i use the 75mast. i have used both masts in downwind mode and have found both have their advantages and drawbacks. The 900 is more forgiving in big bumps but i find it harder to get up foil (i'm guessing its because the wing is deeper in the water) and the 750 is easier to get up on foil but on big head/shoulder high bumps breaching can happen. As far as wing sizes i use the 1000HA in high wind and the 1010 lighter stuff.

Whats the best mast length, i'm looking for recommendations

Cheers Bender

What do you recon about an 85cm? , I've been using my surf mast which is 72 and the next option for me on Armstrong is 85 or 100.I used to have a 90 on my SS and it seemed fine, but I think 100 is too big

I only use the 75 cm mast, haven't tried 900, like you said it is supposed to be harder to take off so I would say it is mostly for windy days.
I just ordered a 85cm (not Axis, a custom carbon mast).

I just changed from a 75cm Axis mast to a 82cm Gofoil mast for paddle downwinding. I didn't find it any harder to get started in lighter wind which would be the main concern with a longer mast. On the plus side it's less likely to breach and I can still carry it to and from the water. I wouldn't be able to carry a 90cm mast.