I used 1/8" plate for my base drilled 4 holes through the plate and my foot control. I put a piece of 1/4" flat bar stock under the foot control and bolts from the plate through the foot controller. I welded a piece of 1" round from the base to the height I wanted. Braced the upright bar to the front and back from the foot plate. I then attached a brake controller from a bike system, ran the cable down the inside of my tubing and then back out again at the bottom to a lever assembly I welded up on the base plate. See the pictures I have attached below for more information.
Close up of the lever assembly