Well, since Gamestudio is your target in your production chain, you should make the measurement there. So, lets say, you decide for 128 quants = 1 meter (or whatever you measurements looks like). Then make a cube that is 128x128x128 and save it as MDL mesh. This is your reference for your modeling work being imported into gamestudio. Now export the mesh to a format which can be read by your modeling application (e.g. FBX). Check your import/export options in your 3rd party app so that the import/export scale is matching the reference scale when you import the models into gamestudio (if you are unsure just import the cube and export it again and load the exported file into MED and check if the cube is again 128x128x128). Use as less convertions as possible.