as a heavyweight (100+kilos), in a typically light wind area (Montreal), my boards and sails tend to be large. My boards are Fanatic Ultra CAT longboard, AHD FF 160 liter/79 cm and Fanatic BEE LTD 124/63 cm. My current sails are MS TR-4 10-oh, MS-2 8-oh, Gaastra Flow 3X 7-oh and an old Simmer WCR 6-oh. {MS = MauiSails :-)} All these sails are cambered... I used to have a MS Pursuit 8.5 with NO cams and liked it...It was replaced with the MS-2 8-oh. Last summer I used the 7-oh about 5 times - and the BEE even less. It is still a very good sail and it fits well on the 490/75 MS mast.
Please be patient , I am getting to the question. :-)
When I look at the numbers , it seems 10-oh,8-oh, 6.4 and 5.1 are a perfect set mathematically. If I barely use a 7-oh, why would I get a 6.4 ? NOTE: last summer was NOT typical - usually get SOME good winds. I was hoping to replace the 7-oh instead one day - with an MS Switch. My issue is money. It would require a mast as well. Does it make more sense to replace the 7-oh when it dies or invest in a 6.4 now/eventually ? Which is the better quiver since we do have light wind summers:10-8-7-6 OR 10-8-6.4-5.1 ?