Dougal, a short quick answer you can't merge the Capt Sim with HJG and never will so forget trying The HJG models never had a VC only 2D. Reason? Its the models and how they were made,. HJG is a MS2004 model which will run in FSX but the models were built using a different modelling program and methodology than is used in FSX. This comes up time and time again on various sim forums. It is very complicated to explain why but the mesh design, texture mapping and coding is not a match and cannot be. You can't decompile the older models because unless the keys and data coding is provided to you by the designer you end up with garbage. Even if you could do that you would still have to design the  VC from scratch and that is a major major piece of work. There is a way of looking at the models (a program on the net) but that is all.

Now a question for you, why on earth would you want to do that anyway? Why not use the Capt Sim model?