>Do I need to try and fill the hole with epoxy and redrill?

That's what I'd do. Take the extra time now to fix it right and you'll be a lot happier in the long run. If you fill it with silicone and it later starts to leak, then you'll be messing with it again.

Also, if the hole is slotted in the wrong direction the screw won't be pressing against the side of the hole (just silicone) when you press against the foot controls. Only one of the screws will be taking the load.

When re-drilling, start with a hole smaller than the final hole size. That way if you need to pull the hole later you can before reaming to the full size.

Just my opinion, for what it's worth.

Dale