Easy way to make an arm:
1.(1) Electrical 1/2″ conduit hanger 2. (1)1/2″ 90 decree bend conduit 3. (2)1/4″ x 1-2″ machine screws 4.(2)large washers 5.(2) 1/4″ wing nuts
Vex may have to drill small hole, marcum/lawrence use existing hole. Wing nuts allow easy rotation of clamp and extension of arm.
Heres a pic w/arm extended: