MorganS:
My favourite for beefing up a trace is to just puddle solder along the whole trace. Specify the soldermask layer to leave this trace un-masked.For bigger current, lay a copper wire along the trace and solder that down all the way along.
I was thinking about doing this, or even adding more copper. make it 4oz.
I think for the first run I will go with the un-masked and see how much I can push it till it fails.
The funny part is that we will use this part of the board more in the first two days of commissioning, that means 5 or 6 times. than in the next 5 years.