[b]John:

Did a little looking myself, discovered an oddity.

The [link=http://restored-classics.com/willy/page6.html]Knight Aero[/link] used two sleeves in a single cylinder. I have never been into one, I thought it used the single sleeve as did Bristol and Napier. Click the link, there's a good description of the two sleeve system.

[link=http://www-g.eng.cam.ac.uk/125/achievements/ricardo/page36.htm]Here's[/link] a single sleeve single cylinder development engine. No details, just a picture. The caption is interesting though.

[link=http://www.geocities.com/kiwiengineer2002/sleeve.html]Here[/link] is a good explanation of the single sleeve engine, with diagrams. A bit hard to get through uless you already are familiar with this design, but give it some study and you'll get it.

Bill.