Prepare by purchasing like a Hughes Autoformer or similar
Devices like the Hughes only correct voltage in one direction - up or down. The only one I have ever seen that corrects both up and down is the Sola Basic I mentioned in my original post - we find places we have to use it in the US as well.
We bought one of the ISB Solar Basic Voltage Regulators a few years ago in Mexico. I find I have to use ours in the US as well. You would have to use two of them to regulate both legs of a 50 amp connection. I know there have been any number of products mentioned over the years on this forum but this is the only one I have ever seen which can correct both high and low voltage. They work. I have never been able to find one in the US for a decent price.
Corrector of Voltage 8 and 4 KVA
http://www.isbmex.com/productos/corrector-de-voltaje-8-y-4-kva
Rated capacity: 4 KVA and 8 KVA
Operating range: 85 V ~ - 147 V ~
Rated voltage: 127 V ~ 60 Hz
Maximum current: 30 A (4 KVA), 60 A (8 KVA)