A little off topic,
recently got one of these engines off a 'net auction at reasonable cost, an early 1960's Cox .15 Sportsman engine. It was Cox's largest reed valve engine, it powered their Piper Cherokee RTF control line aircraft, but also was sold separately. It was one of the largest CL RTF's as most during 1950's and 1960's were half-A. Cox, Wen-Mac (acquired by AMF / Testor), Aurora, etc. (I recall UK had a couple of their own half-A RTF's, too.)
Think I might put this in a Midwest 33 inch (840 mm) wingspan profile Warhawk control line aircraft.
Also recently picked up a venerable 1950's Fox .09 Rocket engine in good condition. Freed up Castor engine drag with some light machine oil. They still sell Gunk Super Oil, but now in a plastic bottle. My can is probably now a collector item.
Peter Chinn's engine article in the Sceptre Flight engine test archives put the Fox (0.99 displ.) at 0.11 BHP at 14,000 RPM on 20% nitro, optimal prop was around a 7x3, (maybe a 6x5), not bad for a side port engine. It only weighs 3.1 oz., which is very light. Some thought it was equal to a Cox .049 Babe Bee, but they probably had it propped wrong. Would be a good upgrade for a .049 trainer to convert into a good sport plane. Some hacked off the approx. 7 cc tank but did a poor job, This wasn't necessary, as it can be bulkhead mounted.