What about something like a walden mega magic, at whatever size suits. Still heaps of volume.
I suspect you probably can move to something like a 7 ft2 and not really notice if you get the right board. I have a 7'4x22.5 x 2 5/8 (I think..it's definitely 7ft4) and it paddles almost as well as my 9ft2. It doesn't catch waves as well, for sure, there are positional things I had to learn, and it's no where near as good on thigh high or smaller waves nor does it 'glide' in the same way.
But the trade offs are not particularly big and there are a lot of side benefits from it being shorter.
It is a flat rockered at the front, but extra tail rocker for beach breaks, widish nosed board with hard rails for the last 1/3, so it's not just the dimensions that are creating the 'almost longboard' result but still allowing much more manoeuvrability. there are a lot of design features involved. It's a custom built so won't be in your shops, but the shapers website has some details (he is a bit hyperbolic but through passion, absolutely fantastic guy)
http://www.grantmillersurfboards.com.au ... powerglideI suspect getting a narrower board, around 21 inch or so, might make some difference but not much. It's still going to be 8ft long and require movement around rather than just weighting changes. Of course, if you are sticking to biggish waves it might be fine
Go for a wide, fat, fairly flat rockered board with some performance tweaks. Stuck with the fun board shape. Well, Worked for me anyway ...