Jeff, have you cracked open any of your eggs from the X hens to see if they show the bull's eye that fertile eggs have? That's the easiest and quickest way to check fertility. Then if you don't have any bull's eyes, you know something needs to be done to help.
Given the size difference, I don't know if trimming vent feathers on the hens might help or not, but it wouldn't hurt anything.
I don't want to AI either, if they can't "do it" by themselves, I'm not gonna do it for them. I agree, a sustainable bird needs to be able to reproduce without intervention. I guess feather trimming is an intervention, too, though.
However, even if you do intervene on the first cross, the offspring from the cross may be able to breed just fine.