drsteve,
A portable is easy to ship back to the factory. Not all of us want to start pulling things apart to fix them.
I don't find the protection offered by any of the current crop of surge devices fit my comfort level. Low voltage cut off is too low. High voltage I've never seen. The Sola Basic autoformer does both boost and buck, and nothing that I can afford will protect the RV against a direct lightning strike.
I use an autoformer, which is equipped with surge that is about 20 times greater than the PI and a Magnum hybrid inverter charger for correction of low voltage.
Before the 30 amp RV is connected to any shore power, I do a polarity check, and a voltage under load test.