This is not to throw cold water on your comments --
cylinder fin technology -on air cooled engines - is very old -
The standard for years has been to use lots of fins -which "radiate" the heat.
Also most of these large engine setups used steel fins - lots of em -close together and inportantly, a close fitting duct work which insures that the air passes thru the fins --not around the fins .
Many new model engine designs have reduced fin count- and on the engine you mentioned - shorter fins in reduced count.
should it work?
of course - as aluminum has very fast heat transfer -
But you have to have moving air flow for any setup - not the tight ductwork on the early on steel fins - that close spacing , created a heated air layer which effectively insulated the barrel and the cool air -if not forced thru the fins -simply passed on by-----
On current tech engines, as long as the plug and upper head get good flow - and the fuel mix is right -- the aluminum jug /gas engines will not go into thermal overload.
I think the last of the steel finned model engines were some industrial conversions. Kioritz I think was one
The wide fin spacing used on current designs (most ) ,allows the air flow between the "fins" and that is why the technology works, without close fitting ducts.
(you already knew that stuf tho --)
There is a fair bit of "Danger Will Robison!" warnings on 3D flying - , suggesting duct work is required to cool twins, due to low air flow-
One real reason is that constant hovering puts a higher load on the engine -and if you lean the mix - you may get free smoke -