Cycleops Al rollers resistance unit fitting woe

Cycloslalomeur

So it turns out I'm too thick to fit one of those magnetic bars on to a set of Cycleops aluminium rollers. I've followed the instructions religiously but the bar rests against the drum on all settings except 0. Any ideas as to what I'm doing wrong? I've emailed the "manufacturer" (handmade in US my ar5e) but they have yet to reply.