I always tend to do sub-assemblies as I hate making life difficult for myself with reaching a paintbrush into tight spaces.
I have magnetized solar engine upon Bastiladon, even skinks are magnetized with 1mm magnets in the hands. I don’t see how to subassembly carnosaur , you may do it with the stegadons howdaw eventually. I did personally only with the engine of gods. Consider however that I have old models from 6th edition that are smaller than the new ones (except Bastiladon .. there is only one model)
My carnosaur and Slann are not attached to their mounts, the rest I just did because I like to play with him and blu tac is annoying