would it not be better to import the model in the 3d modeling package that you use and do it that way ?, i think you didn't make the model by the sounds of it so you should be able to do it you're self ..

I have been rotating my meshes during transformation as a quick fix but I'm not quite sure if I should continue doing so.

Trying to endlessly switch/convert between 2 different coordinate systems will just mess you up and may make you introduce a bug in a different class (or, and this is much more probable, in concatenation of the transf.Matrices), just because you are still focusing on coord.system.

Fix the problem right at the source - is the file in different coordinate system ? Then apply all the transformation right after you import the mesh so you don't have to worry about it anymore.

Do you have lots of meshes and don't want to do all those calculations at start-up ? Then , right after you import and transform to a correct coordinate system, save the transformed vertices and you will be 100% sure that coord.system is never the problem anymore.

I would expect handedness to show up with models appearing inside out, as the tri indices would all be wound backwards.

What's even worse is that different gfx APIs define the default backface culling differently.

Meaning -

1. INPUT : There is the first combination of Winding Order and Coordinate System of your gfx package (3dsmax,maya,softimage,blender,...)

2. OUTPUT: And there is the second combination of Winding Order and Coordinate System of your gfx API (OpenGL, DirectX, XNA, MESA, ...)

I would strongly suggest to take the time and Literally write down :

1. the Winding ordering for both input/output

2. the Coordinate system - EXPLICITLY - where each of the Positive halfspace is oriented (e.g. Z-Axis towards the viewer, Y-Axis Up, X-Axis Right), for both INPUT and OUTPUT, directly into the source code for later reference. If you really think that you're going to remember it after 18 months, then you're in for a dissapointment.

While messing with the Coord.system, I strongly recommend to turn the culling off altogether and fix the Winding issue when the coord.system is taken care of.

Example : Importing mesh from 3dsmax into XNA.

- exchange Y and Z coordinate

- invert Z coordinate (due to XNA's coord system)

One more thing - a very common mistake is to forget to do the transformation on Normals and it may take quite some time to figure out something is wrong with the lighting ONLY under certain angles and make the connection to untransformed normals.