Surprisingly, to me, with careful cutting to the lines the windows do actually fit!

 Before moving on with the cab of the tractor unit of the IBG Scammel Pioneer Tank Transporter and Crusader tank kit I used the opportunity to fit the 'glass' parts, These are actually clear plastic and the windows themselves are conveniently marked out on the supplied sheet.

Surprisingly, to me, with careful cutting to the lines the windows do actually fit the recess in the plastic window surround.

I used some gloss varnish to secure the parts. 

Once dry, I can get on with assembling the cab parts along with the steering wheel and its column.