Yep, I have an 8'6 G2 Gun which has served me very well. The in my avatar is an 8'0 fun gun... I have a 9'0 Merrick too.
8'0 x 21"1/2 x 3
8'6 x 21"1/2 x 3 - but this is thinned out, rolled deck, and feels more like 21 or 21"1/4 x 2"7/8.
9'0 x 20"1/2 x 3".
Can't go too far wrong with a G2.
The 9'0 Merrick is a great board. True big wave gun. Very low exit rocker, which increases your speed and decreases the manoeuvrability. (Big word that!). So when it gets really solid I usually have my 9'0 and 8'6 in the car. When I think I just want to survive the drop, and point down the line, I choose the 9'0. A real shooter. If it's solid but playful, the G2 gun gets the nod. Not quite as fast, but greater manoeuvrability, and carried more speed through the cutbacks.
The fin set-up that McT gives you in the G2 is perfect. GXQ sides, and 7" roughly on the centre fin, maybe 7"1/2. I've tried full size side fins, and the full size fins don't release (rail to rail) as easily as the GXQ. Beautiful rail lines and subtile hips on the G2. The long rails give you plenty of rail drive, so you're not desperate for drive out of the fins.
What else do you want to know!

Kidding!