The trouble is, if you go for the 460 mast then you generally have to take down 2 masts every time you go sailing, because if the wind picks up a bit and you need to use the 5.anything then you have to have a 430 mast.
I find this is a pain in the butt and I think it's one of the things that prompts people into taking up wearing boardshorts over their wetsuits, i.e kiteslopping.

So, if you only want to take the one mast then you can get away with a 430 with a 300 to 400mm mastfoot extension. But ideally, the 6.something sails would work best with the 460 mast. I spose it depends on how serious you are about your sailing.
My saving grace is that I am a sufficiently crappy windsurfer that it hardly makes any difference to how badly I sail, so I use the 43o with the long extension.
It only affects the curve profile in the bottom section of the mast and since there is very little curve in this section then I think it makes little difference unless you are on the top pro windsurf team,.. and I am not.