Ok, so I set out to balance my GP Ultimate Bipe tonight. Pulled out my trusty (it worked for my Avistar) GP C.G. Machine, only I can't use it since the upper wing gets in the way. So using the unscientific (read $0.00) method of holding it, it balances at the 2-3/8" recommended point, but the tail drops ever so slightly. Move my fingers back 1/4" and it seems perfect. Should I worry about this or mount the battery where it is and go flying? (When the weather warms up of course.)

Also, I haven't painted my cabane, gear, and cowl yet. Will the paint add enough weight to make a difference?

I balanced my GP Ultimate with a GP CG machine. I put wood blocks under the back of the machine to tilt the upright rods forward so that they cleared the upper wing. I had to clamp the machine down to the work bench to keep it from falling.

When you balance it you should use the small level that came with the CG machine. Put it on the stabilizer and make sure it is level when supported at the recommended point. The Ultimate can be difficult to balance by eye.

I balanced mine using my fingers and its fine. Flies great both slow and fast but I think its heavy. Not sure what it should weigh or even what it really does but it feels heavy. Watch out for overheating! I'm running an OSFX 46, bison pitts style muffler.

That's the exact combo I have in mine. It weighed in at 6.5 lbs.

For entry air I have the cowl opening in front of the head (right side of plane), and there's about 3/16" gap around the spinner. I had to carve a lot of the cowl in order to get it over the muffler, so there's a large exit area. I am hesitant to cut the left cowl opening since I'd rather force the air over the head, but I was thinking of opening the small scoop below the spinner. What did you do?

I opened up the entire bottom of the cowl from the muffler back. Left the sides real tight.
I had a real problem with overheat and lean running most of the year. Kept increasing the openings in the front with no improvements.
Then at the end of the year, I plugged the opening on the left side (opposite the cylinder)and it seemed MUCH better.
Only got a few flights and then ran out of season. Waiting on spring to confirm but I think so.
Love the plane, flies great.