I originally started planning little screw jacks on all thread with a tiny electric motor from a drill.
But it would need guides to slide down. All sounds too complicated. So 3 cup square bolts so they dont turn in slots is quick and lightweight.
I stole the idea of a moving pedal box from a pic I saw of a chassis from a new Morgan 3 wheeler. But they had pre determined positions, not slots. Looked like the bolts come through the underside of the floor too.....not ideal.
I really hate chequer plate, but I have loads of it lying around, and it really works by gripping the pedal box when I tighten the bolts and stop it sliding backwards when pressing the brake hard. I dare say you don't want the pedal box moving when going down the road.
Again space is expensive real estate here. The dog leg bends to the right of the accelerator allow the pedal box to fit past the roll cage and give me space for my hooves.
I'll take some more pics when it's in situ.