The only person I know who flies well with Skif 9,5cc is Albert Garfutdinov from Russia. And of course Strakhov who builds them. But I've only seen ones with square cylinder, have to ask Albert what this is exactly.
But it runs well and sound is really nice.
It's special because of Scnuerle scavenging and that it needs a prop with lots of pitch, like 8...9"
Looking at the pictures, it seems to have a ringed piston but I'm not 100% sure, I'm waiting for Alberts reply.
Made in Samara, Russia.