John, I wish you the best on your hybridization plan. Sounds great!
Hybridization plan???? LOL. No plan involved. Just the way it has turned out. Fortunately for me, like you with the GSF, it is not an earth shattering disappointment. I have learned to like the hybrids a lot. Mostly because they grow to a decent size fast and are easy to catch.
I guess I had considered creating some RESxGSF hybrids, but as it turned out I got some by accident so I never really specifically did anything to gain the hybrids. I just accidentally had the conditions for them to happen naturally in significant numbers.