FfarquharDeveloper's TrackMaster Customs

Merlin:

So last year I made a Merlin for a client using a Gordon Body and Henry Tender (albeit in green with a flat drive converted by the client) and now I'm doing that this year, but for myself, and more in-line with his on-screen counterpart, but to my liking.

Does that mean they somehow managed to install the self contained flat drive instead of the original C tender unit? I knew they looked similar but didn't know the flat drive would fit (at least not with the battery in). Would the shell of a Henry tender fit on the Edward/Gordon/James chassis, or does it have other differences apart from the side frames? Either way, that could be the first time I've seen anyone doing this mod.