So.... really you don't want to attach them to the floor, you want to attach them to your chair.
Screw the pedals on to a base that is wide, wider than your chair so your feet don't get tangled.
Attach some kind of cord to the base with a hook on the end, once you get settled in your chair, reach down and hook the cord on the shaft above the wheels of your chair.
You can push as hard as you want and never move. Rubber would be best for a bit of give so you don't destroy the pedals.
A pair of wide bungee cords would work great, they have a hole at one end to screw onto the plywood and a hook on the other.
Might be awkward if the doorbell rings though.
And if they ever break ..... POW. You are gonna hit the back wall at 20kph.
Concussion, twisted neck from your headphones....
Explain THAT to the insurance company.