modelling prob

[st1]

hi, i'm new here :-)
i made a car body in max. I made doors this way:
1. selecting the edges that are around the car and chamfered them 0.2
2. extruded the edges -1 so they are deeper, so the doors look independant when I render the model.

But now I have a ploblem with smoothing the model. I've put polygons of the door in material group 2 and the ones of the space between door and body in 3 (body is in 1). Then I used meshsmooth (iterations on 2 or 3). But the problem is that the polgons get smoothed and the gapp between the doors and body gets stretched so it variates in weight. I've put the option 'separate by smoothing groups' on.
Here is what I tryed already:
1. give vertexes and/or edges a higher weight, it has a bit of effect on 20, but not what it should be
2. chamber the edges of the gapp again 0.1 (even with a 3rd time 0.05) but that doesn't do it
3. both 2 & 1 combined

Anyone can give me a hit what to do? I find a lot of tutorials about car designs but none of them give a good explanation on how to use teh meshsmooth on a models doors (and simular parts)