single leg RDL's. the weight will be light enough it will have almost no effect on your back or grip but they will kill your hamstrings and glutes. however, it is light enough load on your CNS and back and grip that you can add them in on top of everything else without worry. single leg glute bridge are also awesome.
add in some super heavy shrugs once a week and use alot of momentum.
if you have access to a cable machine then pull throughs will help alot. if you have access to a leg curl machine then those are also really great. leg curls are the one thing that i think most CF could really benefit from doing. sort of like bicep curls they get a bad wrap for no reason. obviously GHD are great, but too many people don't have access or aren't strong enough and do them wrong.
edit - i really like doing single leg RDL from an elevated box or standing on something. if you don't have much to stand on then using smaller plates (like 2 25's on a side instead of one 45, assuming steel plates not bumpers) can work good. using dumbbells and standing on something, even a bench or the end of a treadmill, can work great. but the point is the deeper you can get that stretch the better. using a trap bar can work great for this for balance if on a box. once you get really good with the stretch or if going from the floor, elevate the toe to really help strentch the hamstrings.