I dont know anything about the superwhing that is not commonly known and have been posted on this forum. I do know that a die will wear out over time and that the later batches will have thicker walls. I would think that is the issue here? The superwings are made by Goodall and not the F16 class so we dont have complete control over them.
£500 for a bare carbon tube from JohnP?? Whow, that is a good price. Unless you really want a wingmast or an alu mast, that sounds like a really good option. I dont think there is other reasons for not pointing you in the direction of Stealth Marine and JohnP than simply not thinking about it or not knowing the price. After your posts about the issue, I am certain others who ask about mast tubes will be informed about both options. Dont help you much unfortunately. Unless you build another F16 (a DS-F16 would be very interesting. We need a hard chine design) and sell the Blade. Probably not a very attractive option for you at this time.

The largest difference I see between the A and the F16 is the spi. Personally, I dont want to go back to a non-spi boat in our dominantly ligth-wind area.