Experience with FAB Defense buttstock?

FAB makes a buttstock with an adjustable cheek riser. I know you can't pull the charge handle with it fully lowered. My question is how much I'd need to cut off the front of the riser so I COULD pull the handle with it fully lowered and the stock in the shortest position. It's a longshot, but I'm hoping someone here has some insight.

Link to the stock in question: https://fab-defenseus.com/glr-16-cp-...le-cheek-rest/

Alternatively, does anyone know of a buttstock with some sort of cheek riser that can be collapsed to the shortest length and still allow use of the charging handle? I've been hunting for something like this for several years, and the FAB thing is the closest I can find to what I'm after.

I think I've got a fab defense stock running around. I'll look.

Have you looked at the LaRue risr?

Luth-AR stocks. What they have, look nothing like the FD ones. But they work and no issue using the CH.