Windsurfing & Stand-Up Paddleboarding in Michigan
I'm 90 kg, and would not recommend a 110L board for 7.5m2. I think you need something in the 120 L range for a sail that big. I sail 8.0 and up on a 77 cm wide board; 5.8-6.9 on a 116L board; 5.0-5.8 on a 105, and 5.0 and below on a 95L board. At 90 kg, you probably won't go smaller than 95L, unless you're in Maui, and even there I'm on a 95L. YMMV
The jump from 7.5-9.0 is small an you can use the same board for that sail range. The 5.5 -7.5 range is pretty big for a 90 kg guy and you probably won't want one board for that range.
I've ridden the Geckos and the magic rides, but only in Bonaire with small fins, so my opinions on those would not be valuable.
You touched on one of the real problems. I take about three windsurfing vacations a year, in part hoping to try gear. At some of the Vela locations, you can try new-ish JP gear. At some of the Caribbean islands, the gear is old or you have to use small fins. The shops in Hatteras just shrunk by one, leaving only just one shop with new gear, albeit limited in selection. In Maui, you can really only try new-ish JP stuff or Goya, and of course you're not going to be on the sizes we all sail at home. In Hood River, they have the best selection of gear, but again the guys are on 4.5's.
To add to that, if you're at one end of the weight spectrum, you can't really trust the reviews in the European magazines. I've been through a lot of boards trying to find ones that I like. This year, I finally went custom and that's a huge gamble. What's a poor windsurfer to do?