Another minor update:
Measured the current draw of my bike today, using work's DC clamp meter.
It peaks at 15.9 or 16.0 amps. The controller is rated for 18 amps, but it's not getting there.
So 16 amps x 54v = 864 watts being pulled from the battery. Looking at Brett's GL2 graph (same manufacturer, but mine is smaller diameter), which drew ~850w at 48 volts, and delivered 525 watts I guess mine is in the same 500-530w at the wheel range (but less torque than the GL2).
I'm planning to add material to the current bar in the controller to get it to 18amps
My battery is rated at 2c (10Ah), and has a 20amp fuse. My lights draw 1.7 amps. So hitting 18 amps should be ok.
The only catch, is I think my battery is not delivering the Ah like it used to, it's 6 months old now, used for 30-43k every work day. I've run out of batteries twice unexpectedly, on very windy days, but I still suspect it. It went flat at ~45k today, instead of 50 or so. I guess that could be the wind.
Maybe I should upgrade the batteries soon - 40amp current capability would be nice
I also fitted another Schwalbe Marathon Plus to the rear wheel - these tyres rock. The front Marathon has done 3500k without a puncture, while the Maxxis Overdrive Kevlar I had on the rear wheel has had 4 flats.