You do not say who fitted the screen for you. Was it a reputable company like AutoGlass who fit the screens that are OEM, or was it a cheapest option company that the insures love to use if they can get away with it?
Some time ago I had two rear screens put in by a cheaper option because I ded not realise that my own widscreen cover actually meant that it covered all of the glass in the car, not just the windscreen. Point is both went bang within weeks of each other! I then called into the local AutoGlass and they told me that my Comprehensive insurance covered all of the glass in the car, sides too. They fitted the rear screen whilst I waited and that has now been in for ages as far as I know because another oofer bought the car from me. As we keep in touch it is still the same one too.
Anyway m8, it sounds like you have probably had the same experience as I had before I used AutoGlass.
They fitted all of the necessary trim bits new too.
With migs two types are fitted too. They are different for cars with AirCon and without, as is the rear one too.
The screen should come with a warranty anyway.
Mine is a;
GUARDIAN
Laminated
DOT22 M55 AS1
43R - 000305
E9 Transp. 75% Min
*****
No rubber blocks are used under the glass, some temporary ones might be used to hold the glass in place at the bottom of it until the adhesive sets (about an hour, then the car cannot be washed for 24 hours). The blocks should then have been removed before the trims were put back. Nowadays AutoGlass use an adhesive tape to hold the screen in place by sticking it to the screen top and roof, then the sides and once the adhesive has a hold they take it off. It leaves no marks at all.
Hope that is of some help
