Excellent questions. See the information we have about this in the lengthy thread about hybrid bluegill (HGB). There is a post or link about FX generation HBG. See info from member called Meadowlark. He was following sequential or generational HBG in his ponds. He reported still good growth of FX HBG after a few years. However, he no longer posts on this forum.
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=256325#Post256325I have a couple of local ponds that were stocked with just HBG as the only panfish and never restocked. From my experience it take numerous years (15-20) for later FX generations to look a lot like GSF. Faithful reporting members here have found that if the predation pressure is always 'strong', HBG are periodically added, and pure BG are also present the GSF revert problem is a lot less likely to occur and is not real noticeable or non-existent.
One problem is this forum is not real old so many do not have lots of long term experience with FX generations of HBG. Since we now have your baseline fish information, If you periodically come back here and report your results your information will definitely help other members.
Here are some of the links from the HBG Archive thread dealing with F generations of HBG.
Dealing with offspring aka F2, F3, F4, etc. generations from HBG:
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=332398#Post332398http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=349990#Post349990More FX discussion.
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=404439#Post404439 
