Hi Ron, I wouldn't give up on the 'negative incidence' just yet - if you look at Pic 'Seagull Edge 540 013.jpg' you can clearly see the wing isn't square with the firewall. This would also explain the 'tail heavy' attitude; it's not that the aircraft is actually
tail heavy, it's just that the fuselage has to be angled upwards for the wing AoA to be enough for flight.
I think the only way to fix this problem is cut the wing slot again, changing the angle of attack of the wing to square with the fuse. Then rebuild/refill the slot and sand and finish it until it looks nice.
Just my thoughts