All my research into this indicated that it's great for FAC .22 (I owned a Royale 400 and agree with this statement) but in .177 at sub 12fpe, it's not.
I haven't owned one in 177 sub 12fpe though. But I do remember reading an article (in Airgun World I think) when they were first released about how they're still working on the 177.
My guess is the physics of the low power, smaller caliber just can't be done. I'm sure they've tried as best they could too.