I previously owned an open Stormforce 6.5 and used another recently for an exam. They're a very impressive hull. If you're looking at Cameo
I can tell you that's she's very clean. Wavelength on here had a trip on her recently and he could tell you more about her specifically. She's well specced and the 200hp should see her clip along nicely.
I like the canopy concept and I think it works well in Irish weather - not so sure about sunnier climes. Keeping it petrol is fine for cruising over two days, your right about the economy for average use. The tank will be at least 180L so you have quite a good range there.
I used to dive out of mine, the tubes in the water make getting back in a bit handier than some others.
Feel free to PM if you like.