here's pics on the brace DH built for my pedal. the wood is 1/2 inch thick on the bottom of the brace and the top of the brace.
this allows my machine to run at half speed (i don't have a speed control button on my machine).
i was having a problem maintaining a constant speed while moving the fabric - i felt like i was patting my head and rubbing my belly.
so he laid down on the floor while i kept the pedal at the speed i liked and he measured that height and then built the brace.