Look carefully at your glass though... There's that major curve from side to side, but I'm not sure how much curve from top to bottom. You could test how well the tint will lay down around the curve by spraying the outside with water, and laying that tint (leave backing on) onto the window, adhesive out. This is how you would trim the tint to rough size anyways. If it lays down around the curve real nice, there might not be much curve from top to bottom. However, if you get some big air bubbles, like big creases coming in from the edges that you can't get to flatten out, you've got too much complex curve. At this point, with the tint laying on the outside of the window, is when you would start shrinking it with a heat gun. Try to get those large creases that come in from the edges out with the heat gun. If you can make it lay down completely, you should be home free.
You might want to buy some cheap tint from an auto parts store to test this with, but don't actually use it! Order yourself some professional quality tint and it will last a long time. I've ordered tint from these guys multiple times, and it's great stuff. http://www.sunshieldfilms.com/index.php
I've had their tint on the side windows of my 2003 Silverado since new, and it still matches the factory tint perfect. No turning purple like the cheap stuff from auto parts stores. Also- last time I ordered they had 20" tall bulk rolls, and 40" tall bulk rolls. Go with the tall stuff and it might make that windshield much easier to do.