polymodeling

[Razor-]

I am using 3DsMax 6, polymodeling.
I am modeling this phone. I made half of it and I mirrored it and weld it. Now I must do the light from the upper part of the phone (left). I mean the light that is part of the phone, that little round thing there. I would do this by cutting the polygons along the light and deattach the polygons that will make the light. Copy the edges and chamber some edges... you know the technique.

Ok, but the problem is that doing this the shape of the phone will change, the round part of the top of the phone gets less round. This is because I had to add some new edges there to make the light.

How can I make that light without changing the shape of the phone?

I attached a picture whit the phone.

Image