I have heard of some ppl getting a/m sunroofs and personally dont see the problem myself.
The sunroof has structural supports when fitted anyways, as I had one fitted to my MY04.5 Opel Corsa from new.
I do think it would affect the stability and handling in a little way, but not enough to not get one.
Hopefully someone with a little more knowledge can shed some light on this.
Happy Motoring
duglet