I couldn't sleep, too damp warm, so my head kept spinning around this.
A: I remembered there is a topic around here to create custom shapes with Hype's build in elements by adding and "substracting" you can get pretty far. But, I just looked and cannot find that topic.
B: So back to my warm bed... I came up with the idea to cut up your image(s) to keep their "footprint" small so to speak.
After experimenting with it this morning I realized it was too cumbersome to be effective.
But thinking back to (A) and combining that with (B) I came up with this idea:
Just create a rectangle, give it the action you need, then copy/paste and resize it to your needs.
It's not purfect but it gives you more control of the "box" that triggers an action and a smaller ""footprint so things get easier reachable behind it.
Edit: duh, I forgot you can rotate stuff...