Gluing vacuformed windshields

Hold the window in its place, then take a brush and run a bead of a high quality white glue along the edges and leave it for a day.

i use "weldbond" brand here in Canada. 

I agree with Don - use the groove, it's there for the placement. I use a white glue dirivite called "Jewel glue", a craft glue with various actual uses.

Also, if one side does not conform and stick, DON'T PANIC! Leave it and consentrate on what does stick, hold it down and make sure it settles. Go back to the other side when that has properly cured and just hold that down. Otherwise you'll make a semi-transparent mess.

Some kits have a little groove or flange, in which case you can use white glue or those white glue derivatives made for transparencies.  If no flange or groove you need a really strong bond- I use epoxy for those.  I also drill a few holes with a very small drill- just a few thousandths deep- down into the plastic, to get a better bond.

It seems that there would be very little area to glue a vac windshield without leaving some glue tabs under the roof.

I've dealt with clear plastic film in autos before. I used clear parts cement on those and it worked fine. Future is another option but I don't know how curvy your windshield is or what you're putting it in. You got any more info?