Hello.. Its been an awful long time since i have been on the forums...
Anyway, back to the question. Yes i have used animation master to make things for fpsc, however there are several things you need to remember.
First of all AM cannot export .x files, so you need to right-click on your object, go to the plugins option, choose export, then .3ds. You can export your model as 3ds format but you have to reduce the number of polygons per patch to 1 or it wont display correctly in fpsc.
Once you have done that you must then use another modelling program to convert the 3ds file to .x.
Hope it helps,
Wizzkid