If this is a model for FMS 2 alpha 8.5, then when you make a Metasequoia model using Meta LE, you save the file as DirectX with the modelname.x file name. Then you should be able to copy the other related files for FMS, .wav for sound, .par for flight physics, create a new _prv.jpg for the preview file and usually a _readme.txt file to describe the model from another model.
Open up the copied .par file with one of the .par editors and make sure the wheel points are below the wheels and the ground position is lower than that. Also edit the collision points. After that, your model should fly very close to the copied model.
-- ggunners