I am thinking about getting a 2015 KA 7.9 race sail. Would it work ok on my north sails sting(50% carbon) 460 sdm. I think it's constant curve like most north masts and I believe KA works well with north?

yes it will work . i think the diameter is the same

Maybe not that mast is at least 15 years old, North masts have change a lot since 2005. But you can always try. Diameter is your main problem.

If possible try it, the only way you are going to know for sure. That sail will work best on constant curve up to slightly flex top...ideal is 13.5% bend. As AUS4 said...diameter could be an issue for a mast of that vintage.

On the same topic, I am using a KA mast 490 100% 2012 or 2013 (cant remember the year). So far i am trimming it with the same year's Koncept 8.5. Do you see any concern the mast not to work with 2017 and recent KA.RACE? i am looking at 8.7. Unifiber Mast selector positions KA in the same spectrum in Con Cur chart.

I appreciate all the info. I agree a old mast may not have the best out come on a sail with a 2015 year. My plan was to get something that was powerful for light wind windfoiling....so I decided to play it safe and splurge on a dedicated foiling sail rig

Hi Nikolas....I have no reason to question the mast on an 8.7 Race, it should be fine.