I would highly recommend the large Flirt. The L Spice will surf ok, but you'll battle to get ends...
I'm a bit shorter - 6'4", size 12, but I do paddle the Flirt on the middle, or one forward from middle seat position. It's the biggest play boat I've found (although choice is a bit limited here), and I've used it river running (mostly III, some IV), low volume (easy) creeking and the Zambezi, and been very happy with it. I added some knee-blocks a while back, and found that, together with well-fitting hip pads, this improved the handling and comfort quite a lot too.
Definitely try before you buy if you can - or at least sit in the boat in the shop to see what the fit is like... There's no point having a boat you can only spend 5 minutes at a time in (especially if you want it for river running).
-Dave