btw, thanks a lot for sharing the source code of your EFM, this is indeed very helpful for the community.
Yesterday, I've made a short test of your EFM with minor code analysis. Pretty impressive, however there are some points I'd like to clarify with you (if I may):
void ed_fm_set_draw_args(EdDrawArgument* drawargs, size_t size) relies heavily on the model specific animation arguments and may potentially lead to a memory violation if the size of drawargs array does not match the maximum required by the function implementation. I refer to the latest commit 91a5939f I see on the master branch. On this commit the index goes all way up to 1128 and there is no check if that does not accede the size of an array provided by DCS.
There's something weird about the flap animation, seems to be reversed or something. I couldn't figure out what this is.
The rolling behavior of an aircraft seems a bit unnatural. I didn't check the code, but it looks like the MOI about X axis is not accounted for. Please correct me if I see it wrong. Basically whenever we bank aircraft it acquires a rotational momentum about its longitudinal axis (in case of DCS's convention it is the X axis). When the stick is returned to a neutral position the acquired rotational momentum will continue to rotate aircraft until it vanishes aerodynamically or it is compensated by the flight-control system that applies an opposite momentum by commanding a required aileron/flaperon input. If this is on your TO-DO list I'd be happy to help you to implement that, however this isn't an easy task.
The implementation of ed_fm_suspension_feedback seems to be missing. I'm not entirely sure, but I think we will fail to provide correct ground behavior and gear animation without this function. I believe the suspension mechanics is provided by DCS itself, but I'm not sure.
overall your EFM looks very promising to me. Of course, and I hope everyone understands, that in order to achieve somewhat correct behavior of an aircraft the EFM is to be highly adapted to a specifics of an aircraft. There's simply no way to provide generic EFM to be suitable for all planes. So, in that case I'd recommend to all who might be interested in any further development of this EFM to actually branch out of main/master of https://github.com/IGServal/Basic-custom-flight-model-for-DCS-World/tree/main and NOT to fork from it. That way we will be able to merge the code and keep track of improvements and bugs.