Years ago I built some layouts with GarGraves flex track. The easiest way to install 706 uncouplers is to use a piece of Gilbert track cut to just include the two ties with the 706 clipped on between the two ties. While I have installed a few directly on the GarGraves flex it is harder than it seems. First the bottom of Gilbert track is flat and stiff. The bottom of GarGraves rail has two downward facing edges to hold the wood ties, these need to be trimmed off. Second, the rail can also bend and get slightly out of gauge when the ties are removed and the 706 is clipped on.
I have no experience with GarGraves sectional track so I cannot comment on how it would work. The GarGraves rail is a lighter gauge than the Gilbert rail so using the Gilbert clip on accessories requires some care.
To power the flex track I always slipped 1/4" brass strips into the bottom rail gap between the ties. I used 1/4" slip on connectors to attach the feeder wire to all the brass strips.
