I played around with the CSS of the component, but was only able to get cosmetic changes and not actual changes in how it responds to the mouse.
Every element in HTML is rectangle based, so my guess is: no you can not. Maybe there are options to play with the z-index, but I think it can lead to lots of bugs.
Yordan
I was able to solve it by placing tilted transparent rectangles over the blank spaces, and making sure to layer them on top of the trapezoid shaped image so as to block the hover effect on the areas where I didn't want it. It's kind of a clumsy solution but it works.