Hi, the old windows that were taken out were about 30 yrs old and so were chunkier compared to modern windows. The previous owners had replastered with these in situ, but despite this there was an even amount of frame showing and they looked balanced. To be honest the plastering is not absolutely true, though with the old windows in place, this was not at all noticable, had it been We would have addressed this before having windows fitted. We have checked the plaster since, it is not so out of line that you would normally be concerned about it, but with the new windows fitted it is glaringly obvious that something is out of wack, in our opinion because the window frame showing is so slim that it seems to exagerate the minor faults in the uprightness of the plaster and the window itself. We have checked the new windows they are marginally out of upright/level. What we would like to know is, how you would normally measure/fit windows when the difference between the inside and outside measurement is larger than average? Our fitter says the most important thing is that they look right from the outside and measured accordingly despite the fact he was aware of the difference inside and out. does not matter ?