We've got the same transmission, but the tire diameters are larger on your 790 then my 670. Therefore, the top speeds in any gear will be different. Since my tires are probably smaller in diameter, my 670 will go slower in any gear.
That said, I use the brakes for turning infrequently, but only when I'm in the lower three gears on LOW range. For the 670, 3rd Low is about 3.5-4 MPH. My bar-turfs are pretty wide, so even 3rd Low might be too quick if you've got narrower tires.
I also throttle back (I use the handle throtle almost exclusively) to 1200-1500 RPM's when I'm turning with the brakes. As you can almost pivot around the braked wheel, that's a pretty sharp turn.
More often, I use the individual brakes when I'm plowing snow. This is just to help keep the tractor in a straighter path as the snow tends to push the machine a bit to one side as the back blade accumulates the white stuff.
So...if I were you, I'd try it at really low speeds until you can gain enough confidence or determine when the tractor will lift.
If you use the tractor wheel brakes when mowing (cutter or mower) and throttle back to turn, the cut may not be quite as clean (especially when finish mowing...the cutter blades have greater inertia).