Did you really woke up this morning with this question on your mind?
Not sure but if you switch to a metal Thai cup you might be able to work in a jumping knee to the midsection + cup to the forehead combo when they double over. Would require a lot of hip thrust but it's doable.
Either with a raking motion across the eyes or a toe thrust with a front kick? Has a fighter ever claimed he got injured by this? Has a ref ever called timeout?
Actually now that I think about...screw the knee. Just concentrate on jumping metal Thai cup thrusts to the face. Combine it with the Thai Plum clinch and it's money. Course you'd have to have some hops unless you're going to pull the head down to meet the rising cup.Hip thrusts to the face from top position could possibly hurt too. Possibly the best option if you'd broke both your hands.