ISB Sola Basic advice?

Three of us bought these in Mazatlan and spliced them into our 30 amp extension cords. We also learned that here is a small single turn pot on the circuit board so we could adjust the switching points as ours seemed to switch about 108 rather than 110v. Otherwise , I can confirrn that when you add a heavy load at 115 v, the voltage drops for an instant and then boosts to 120. Highly recommend this for Mexican electrical systems.