Here's the issue I see with doing split bindings on a freeride only non-splitboard. Dampening. Not an issue when you're splitting as you're searching for fresh. That's not the sole purpose of your Flagship.
Look into the Flow Prima or NOW Bindings.
I honestly wouldn't suggest mens bindings. That super tall highback is just going to get in your way and at your weight going for the bindings you're looking at is going to make things worse. You need a bit of play in the binding here and there to let yourself move around to get your pressure and weight in different spots on the board.
I think what you need to be looking into is not stiffer bindings, but bindings that inherently increase your edge to edge performance. Flow's do that with the triangle set up and Nows with the rockering frame.