I ported a series IV (which has alternating offset center lugs) a while back. I did alternating holes, one per rib, so the holes alternate about two inches left and right of the track centerline and fall in front of the respective lug. My thought is you get the most out of ports when they're in front of the lug because that's creating a void under the port as the lug moves through the snow, but I have no way to prove it. I used a 1-1/4" hole saw with the teeth ground off. Despite being fairly minimal, it seemed to make a big difference. Looking at the lug patterns on the 300LX, I'm not sure if I'd alternate sides or just run down the middle. I wouldn't do more than two holes per rib, and maybe I'd start with an alternating pattern and one per rib. You can always add more; hard to put them back! I've seen tracks where someone went crazy, and at some point you're letting more snow in than out and losing flotation. Swiss cheese isn't your friend.