Pavel Tsatsouline's "ab Pavelizer"

I have a question.  Has anyone heard of the ab pavelizer by Pavel Tsatsouline, the Russian trainer who brought Kettlebells to the mainstream?  I bought it to strengthen my abs, but I'm having trouble getting into the groove with it.  If you are familiar with it, I am trying to keep my gluts tight while going down into the situp so that my hip flexors cancel out. but I am not getting stronger.  just frustrated.

 

Does anyone have any advice that would help me?

Without in anyway trying to be facetious, hollow body holds will make you use your abs, glutes and more. 

I love Pavel's stuff, but the core exercises and equipment are mostly a cash-in IMO.  Doing L-sits and the GST basics will do much more for your core and glutes.  If you still need more, you can always add squats and deadlifts.