A question of glass

Heres something i can never get a straight answer to- I plan to chop the roof of my 1971 Rover P6 by 2 1/2", but what do you do with the glass when chopping the roof? Is the screen cut? Someone told me that you simply sink the screen into the bulkhead, surely that cant be the case with all roof chops? And wouldnt that mean you have to angle the A pillars inwards?

The side glass should be fairly straightforward as its flat- im thinkin make a template out of MDF the same thickness as the origional glass, then have it transferred onto perspex. I have a mate with access to the stuff, but is there a certain type that should be used?
The actual roof chopping bit im fairly confident about, and its made particularly easy with my rover as the whole roof panel unbolts leaving a basic frame which can be dismantled further at the A pillars, but any tips on the subject would be welcome as this is my first attempt. **)

Richard, being the genius he is (I owed you one :D ), has given you the best route. Sinking the windshield takes some logistics as there are other systems under the cowl that need to be modified. Not sure about the glass you use there, our methods, on later model cars, are based on a laminated windshield, and tempered side glass.

As you surmised the side glass is relatively easy. Rather than the plastic for the flat pieces, which scratches easily, folks here will transfer the pattern to flat, laminated glass, which is what the older cars came with. Rather than MDF, we use a material that's called Masonite, or tempered hardboard. You likely have the same stuff, but perhaps under a different nomenclature. Same stuff that peg board is made of.

The curved glass is a different matter. Some grind away the unnecessary part, others find an experienced glass guy who scores the new edge and breaks it off, frequently breaking the part to be saved. It's not uncommon to "kill" several windshields before getting one that survives. The back glass is probably tempered and would work better sunk in, or you could use the perspex if you can live with the potential scratches. The old glass would be used as a pattern to mold the perspex over for curvature, then cut for heighth and width.

Thanks for that guys, guess its time to find my very own glass guy and see what he can do.
Yeah it did cross my mind that perspex would scratch easily, so laminated glass sounds like a much better idea.
Have any of you ever tried to do the cutting yourselves? With about 400 years in the trade between the 3 of you (kiddin!) and the amount of chops you must have encountered im guessing at some stage you must of had a go. Is it a real black art? Smart people would probably take your advice and go get it done properly but my aproach to everything is to have a go at it myself, usually resulting in breakin things and costing even more money! But Glass for mine is reletavely cheap and plentiful so i spose ive got nothin to lose! Waddya reckon?
Meanwhile i will get at least one of the books recommended by Tech and learn sumfin.
Thanx