estimate 20kg loss, glass, seals and fixings, and significant as high up weight in car - would have had an exact figure but broke the back window getting it out....well say broke, threw a tool through it in a fit of rage and reduced it to a pile of bling
rear window is an absolute sod to get out, bought a proper bonded window removel tool and it wouldn't shift it - reason being that the rear window is not just bonded in but has a bloomin great rubber seal round the edge also which is also glued in, just couldn't shift it and didn't want to mess up tailgate paint so ended up breaking it.
Rear side windows fairly easy, needed to cut them a bit smaller from those supplied due to the way I have fitted them. I have removed the rubber seals and bonded the windows directly to the metal lip that used to hold the seal. This means that the window is inset maybe 10mm from where it would be normally but I have done some black painting around the window and you cannot tell, looks stock.
Front drivers window I have left as glass so I can open it easily (like window down driving) and passenger side is now plastic just fitted as a replacement for glass, left electric window mech in as are probably replacing the whole door for a fibreglass one soon.
While rear window was out, have taken a whole lot of metal out of the hatch, very light now, so maybe 3kg there also
need to get it weighed at some point, should be getting on for 900kg or maybe even less now