What a fun looking army. I play something similar, though without the extra Vypers and Warp Spiders instead of Swooping Hawks.
How do the Swooping Hawks play?
With all the internet crying over the D weapons and what have you i decided to avoid them because contrary to the bithcing and moaning this book has soooooooo much to offer.
The Hawks are really cool! What I do is start them on the board hidden on turn 1. I then warp them back into ongoing reserves for turn two so they can come in automatically. When they come in they don't scatter and upon arrival they can drop a small blast (5 or less in squad) or a large blast (6 or more models in the squad) on anything within 24" but don't need line of sight to hit it. They also can hit flyers with haywire, have assault 3 guns, can move 18" because of their wings and all kids of shenanigans. They are not amazing by any means but they are a threat to literally every type of unit in some way.