Discovery 1 rear winows - opening ???

I have a Discovery 300 tdi 3 dr, so the rear side windows ( boot ) are fixed solid in place, however when I do get it on the road, which I am currently re-doing the floor, I want to take my dogs in it. Now with a lot of media attention altely and correctly about dogs in cars with windows up etc - got me thinking.

Could I do a modification on both rear windows where they could be opened at the side so as to let the air get to the dogs more quickly, than the old trick of winding your own window down at the front and hoping enough air eventually gets to the back where they are.

Defenders and L200's have sliding windows but are quite big in size, so i'm thinking of doing the same as the passenger rear windows that pull out on a hinge and click style.

My question is it easy to drill glass and has anybody else done it before?

Thanks

My old disco had plenty of built in ventilation!