Kahn,
I just got it this far recently. I haven't run it yet. It had very mild port timing. I lowered the intake port 1/16" to give it 120 degrees duration and I raised the exhust ports to get 140 duration. Mine has a floating ring, so the ports are narrow to prevent catching on the ports. I modifed the piston also to improve flow. I think that you will be happier with a Homelite 25 or a Toro 25 in your 13# corsair. I am looking at a ten pound plane. Thats why I got rid of the heavy flywheel etc. Here are some pictures. You can see the enlarged intake port in the picture on the right.

Dave