RE: Kombat 87 or Evo 90?
If you choose between this two boards is not that hard. The hard part will be decideing on what you want to focus on. I haven't ridden the new 90 yet, but based on riding the new 70 and 80 and the old 91 I can safely say it will handle powered 5.3 at your weight. I'll ask Scotty to comment more on the sweet spot.
The K87 (which I have and have ridden quite a lot by now) easily handles fully lit 5.3 even at my weight (69) and will do it for you to. A sweet board with a sick turn (both bottom turn and flat water turn) which is very reminescent of the Pure Acids. It will not go vert in the same way as the EVOs though in slower waves, more onshore etc it will require a lot better technique to rip. In better stuff it will rip, but in a different way than the EVOs. For me the K87 easily handles 6.4 and I think it will do that for you to with a bigger fin. For backside and B&J stuff the K87 is super nice.
So the choice will be EVO is you have focus on frontside riding and K87 if you don't focus on frontside riding that much and want a faster feeling board that also is more natural in a B&J setting.