We just did this for 9 days and had no problems. We went to the hardware store and purchased a 50 amp receptacle. With 10 gauge wire we wired two household plugs into the receptacle - 1 for each leg. We tied the neutrals and the grounds together. We plugged our device into one outlet in the garage and with a heavy duty extension cord plugged into another 20 amp outlet on a different circuit. With our meters we watched our amperage usage and didn't trip any breakers.
The white label on one of the plugs is to let me know what leg goes to what meter.