Pulled this pic of the inside from another forum- this is the machine, it is a SIP Migmate 150
The input wires are at the bottom right- a brown, a blue, and the yellow/green come from the mains cord. The yellow/green is the ground and goes straight to the chassis.
The brown and blue were load and nuetral labeled. It is these two that expect a +230v, -0v connection. I'm going to be giving them +115v, -115v. Total waveform amplitude is the same, so RMS power is the same.
That is my thinking.