P.S... this might be nothing more than nit picky, but I would jigsaw a hole in your test stand behind the cylinder to allow air to flow through...

People are likely to say it is not necessary, but in a cowled installation the air has to flow over the engine to exit the cowl. (Hopefully) On your test stand, air can exit everywhere but not flow through the engine cooling fins very well. Just my thoughts...

The other thing you could do is just flop the engine over so that it is cylinder up, but then you are going to cuss me because you are going to find out the bolt spacing isn't "square".

AV8TOR