My experience is that the heavier more powerful kart will have an advantage at top end only. The game is to hold everyone off with tricky driving then get a good run onto the straight where you will pass everybody after you hit the main jet. If your track is all tight and you have to gear low you’re in for a real hurky jerky ride.
If you can make the lower weight I would go for it. 4 hole @ 300# would be faster most of the track depending on the lay out plus easier to get back on the kart stand. Just keep the throttle open, keep the fire burning and smoothly drive around the track with great precision. Keep to the inside coming off the straight.
We had a class with 4 different set ups, 2 different engines. Yamaha 4 hole was winning and they kept adding weight to it until it got to 390# then everybody quit. Combined classes are not good because you get the Jeff Gorden effect. Jeffs Chevy goes fast so penalize all Chevys.
FAA certified jet engine and aircraft technician,
Nicholson Speedway class champion 2001,
Yamaha KT100 Service Center,
41 years karting experience