gmax to airport260 and FsDYn conversion

[voscon]

Hi, I'm trying to convert a gmax (flying) model to Airport260 scenery.
FSREGEN asks to use makemdl.ex with the optin to keep all files, but the (new, with gmax) MakeMDL does not have it .
An older version I used did not produce the ..._0.asm file, which is needed, due to using an old MakeMDL.exe.
The real question:
How do I convert a gmax file (exported I assume) to a .APT  or scasm file? (Most popular freeware please if poss.)
Can I (then) use it to make that model in FSDYN for dynamic scenery?  Or is there another way to add a gmax modelto the FSDYN standard models, (e.g. the glider)
(I have also TTOOLS, and some DOS coversion programs that XP does not like) Thanks for your past valuable help!