One huge advantage to the porting if done the way I will describe is much better cooling which there seems to be a lot of complaining about.
How do I know this, from partly self inflicted cooling issues,. In order to build a 360 lb mtn sled with just the little 600 carb engine I took anything that might be excess weight off including the front heat exchanger for about 4 or 5 lbs weight loss counting the coolant in it. (My thinking was on a good day going down a mountain it might have 120 HP and stock exchangers were the same as 160 HP 800's)
I have run ported, unported and now ported again. The last configuration with a ported down the center (small rectangular hole and two wheel axle) and a snow flap I made goes to within a couple inches of the snow got my temps down into low 120's finally with good snow. Before was 140 to 150's.
Why the ported works better for cooling, snow gets in the skid, as the track rolls over the rear axle the snow in there is carried up and thrown up at the heat exchanger via the holes.
Kind of strange to think the little 600 is going away if you look at the new head introduced in 2012. Its a shrink wrapped water jacket modern state of the art head. But even more interesting is the two unused flat bosses cast into the side of the domes on the intake side. Likely for fuel injection is about the only thing I have come up with. Also a odd threaded hole on the top of the head between the two cylinders, thinking maybe for a detonation detector. I have one of the heads and will be reworking it over the summer for my big bore nik-a-sil plated iron cylinders.
I have a goggle bag zip tied under my hood in a high spot on the chain case side. Even with a very well vented hood and side panels it still gets plenty warm enough to dry out a pair of goggles in a half hour. It is a bag made for this, one side is open mesh, came from Western Power Sports
Piston speed is stupid nuts for a pressed together crank in stock form, more stroke = higher yet piston speed with forces
near top and bottom dead center going through the roof. And it will totally screw up your port timing, you'll need someone with really good skills with two stroke port timing software to figure it out or you will end up with less HP than stock. Oh yeah your pipe will need to be redesigned to work with longer stroke for optimal performance.
Highly recommend before you try this you spend $25 for a DynoTechResearch.com subscription which will give you access to read the archived old issues from about 15 years ago. They covered this subject extensively and dynoed these stroked engines with as I remember generally negative results !!