I've just had a play with the 1.16.1 game, and it's soo much nicer than 1.15.4. Much faster and smoother, so I'll work on converting my model for that version. Also, there's an external model mod that another forum member created, and it's a really nice looking model. Especially the rotor head, so that's going to be my focus.

If anyone is playing it in 1.15.4 and finds an issue, still let me know.