In my opinion these cylinders can absolutely be ported and I would highly recommend cleaning up all the ports. I took a dremmel and watched kens video on the how to port and did mine myself. My blasty is pretty well stock, you can see pics in the build section of the forum, my current setup is as follows with this cylinder.
Boysen dual stage reeds with reed spacer
stock pipe no baffel or spark arrester
air lid drilled with 6 screened plugs
260 main jet stock carb needle second clip
wiseco std compression piston
home port job
14 tooth front sprocket.
With all that said it runs like a molested monkey. It tops out in the high 67mph range (thats guaged by being followed by a buddy with a speedometer not radar gun). It will stand in first, second ,and nearly stand straight up in third gear. Im not an expert rider but im not an amature either and I eat alive every 400 4stroke atv I ride with on our tight lil woodsy trails and can even take a couple of the 125 bikes. In a drag bout all of them take me on the back end but I can pull on most of them out of the hole shot. I would ,from my experience , highly recommend these cylinderkits as a cheap option over a yamajug. The namura pistons are personal preference. You either love em or hate em. Personally I prefer to spend the extra cash on a wiseco for peace of mind