The trend nowadays is for heli engines to be missing a key component needed for use with a propellor; the prop drive washer that fits over the crank shaft. IIRC, the 50 SXH does not come with this part. I'm also reasonably certain that the part made for the plank version of the 50 SX will fit the SXH fine. You can order that from The Empire.

As for "shock cooling" due to the enlarged heli head; not an issue, britbrat. I've put a 32 F-H and a 61 SFN-H; both of which have the big rectangular head; on planks and flown them in all weathers with no problems. They just look sort of dorky on an airplane...