Hi Zippi, thanks for the response. That's a nice 60/90 Edge 540 you have there.

I'll definitely consider a Saito. I've heard nothing but good things about their 4-stokes. So, the FA-125A is an option
http://www.horizonhobby.com/Products...rodID=SAIE125A

but since I'm already trying to scrape up money for the servos, it's good to hear that the FA-100 is a good match for an Edge 540 this size.
http://www.horizonhobby.com/Products...ProdID=SAIE100

For comparison sake, here are the OS offerings:
OS .91 FX - http://www2.towerhobbies.com/cgi-bin...?&I=LXBY47&P=0
OS FS-91 II Surpass - http://www2.towerhobbies.com/cgi-bin...?&I=LXSY82&P=0
OS FS-91 II Surpass w/Pump - http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXBY61

Another thing I've read is that 4-stokes run better inverted. Since my Edge's engine mounts at like a 130 degree angle down ( looks like 8 o'clock) that's something to factor in as well. Looks like the muffler angle on the Saitos is adjustable, so hopefully I could angle it so it comes out of the cowl directly under the engine (close to the middle). On this Seagull Edge, there is some major empty space down there to work with.

So with the 4-stoke, I need to get the proper fuel (makes sense), but what's the deal with the fuel pumps? If I get a Saito, do I need a Perry pump or something similar? Unlike the 2-stokes, I don't see a fuel tank pressure fitting coming off the muffler.