Hi, i use gaastra gtx 2011 7.0, 2010 7.5, 2009 8.0 . My impressions are as follows
2011 range is for sure the best. But all of them are quite heavy it the gybes, if you drop to the water the earlier versions don't have a zipper so the water can easily fill into the luff pocket. Very shallow profile so not good in light wind. I don't like the 2010&2009 in any way but the 2011 version (7.0) is, in overpowered, very stable and very fast and feel light in hands in the straights.
I'm also considering to switch to np slalom or race, cause they feel lighter, also very stable in overpowered and better in light wind. Normally they use the sloalom with x6 (But the carbon content is 60% where other brands are 75%). Don't try north warp but a friend who have it also think to switch to np because he feels norths are heavier. Race sails are heavier, cost much more, but if you change your gear frequently, easier to sell,, and also easier to find a good 2nd hand (at least where i live, and also you can get a good condition rs cheaper than a new slalom). If want to use rdm mast, loft sails look good, they design them for rdm and compatible with sdm.