You have all kinds of good gator gar fishing around BCS. When I was in school there in the late 90's we fished Hidalgo Falls (millican falls) all the time. You can click on the link below and get a little history behind the place. Also, might interest you being that you plan on kayaking.
If you can get into Hidalgo just fish down stream of the limestone outcropping there are several "wash" outs in the river. We have caught some monster cats there along with the gator gar. Go to the police pond and stock up on bluegill and fish with cut, live and fresh dead.
The biggest gar I caught was out of the Navasota river off of OSR. Fish was ~ 7.5' long. We fished for cats but caught alot of gator gar.
Hope this helps and enjoy the Brazos!!!
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Coby Denham
Denham's Guided Fishing (Now Retired)