If your tether tests will work on a C6, then you have the potential to later fly it on an E6 (either the expendable or the reload). A few years ago, I took my old 1989 gimbaled engine model, that usually flew on an F10, and flew it on an E6 (8 second burn), using an Eagle Tree Guardian for vertical guidance (In place of the original Sunguidance). It worked, and IIRC the liftoff mass was around 14-16 ounces.
It was unusual though, as the thrust spike got it moving upwards, then dropped to the sustainer burn which was roughly equal to the mass of the model, so it lost a bit of velocity due to drag. And then since the nozzle throat erodes a bit, the thrust drops a bit, so the model reached apogee then stated to descend tail-first for a second or two before it burned out. Then I used R/C to eject the chute. It had reached maybe 100 feet and ejected at about 50.
So, anyway, if you can keep this under 12 ounces liftoff mass with an E6, it would likely fly very impressively slowly to about 150-200 feet.
To me, that's the beauty of gimbaled models, long burn slow boosts, that keep themselves under control. Also, the faster a gimbaled hobby rocket goes, the more trouble it will have with aerodynamic forces, one way or another. Fast guided rockets are best done with aerodynamic controls, not gimbaling.