I think there's a lack of info because there are not a loit of people running them.

One of our club members has the RCV91-CD (http://www.rcvengines.com/rcv91cd_full.htm)
He put it on a Pica WACO Bipe, replacing an OS-91 that broke a connecting rod. He feels the RCV has slightly less power than the OS (same fuel, same prop, same plane) but says the difference is so slight it's hard to detect.

He broke the RCV in on the bench andaccording to the instructions, then put it on the plane.

He had overheating problems with the RCV (without the cowl installed) and it locked up. He called them and told them what happende an0d how he was running the engine. They had him send it in and sent him a new one a couple of days after they received it. They didn't tell him what was wrong with the first one.

He plans to run the new one on the bench even more than the first one. He's very methodical about running his engines and setting up his planes. He's a commercial airline pilot instructor and puts the same attention to details into his models as he puts into his work.