Yeah keep the torque down if using a drill as can do some damage internally as above.
Also, roto's are meant to be pretty hard on owb's too but they don't half make it easy to start. Blacksmith's on fleabay do the sets,
all you need is the mounting hole sizes and owb size I think. Also, someone in the for sale section has a job lot to break, might
be checking what he's wanting?