Hi Dave,
Yeah, you may be in a bit of a quandary at this point. If you go with the later cupola, and have the steel wheels, it would be best to go whole hog and make it a late model, and either change the location or find a pic of a late Tiger I in the Ardennes (that should be fun), or just go "what if". If you stick with the Hybrid Tiger with early cupola, you would have to redo some of the stuff you undid, since the hybrids had (I am fairly certain) early tool arrangement, 2 headlights on hull top, etc. as they were really just early builds with steel wheels and new tracks replacing the older rubber rimmed wheels and tracks, not just older turrets on later hulls. The ball mount for the MG would need some work, they had the large opening for the MG, and a smaller one next to it for the monocular sight that the gunner used to aim the thing. Welsh dragon has you covered on that as well if you want to buy one instead of scratch build it, plus they have a nice MG for it as well.
http://www.welshdragonmodels.co.uk/...le-for-heng-long-tiger-1-116-scale-1318-p.asp
Appears out of stock, but is a nice reference pic none the less
and this one as well, though it doesn't look quite as nice
http://www.welshdragonmodels.co.uk/mg-ball-mount-for-heng-long-tiger-1-116-scale-568-p.asp