MEXICOWANDERER, if you care to publish your design and a parts list, I would be interested in it. I could easily build one and need one for my new RV. I'm like you, if I can build it vs buying it, I will.
I work in the process control industry and we use products made by Transtector. These use SASD (Silicon Avalanche Suppressor Diode) and MOVs to protect our AC devices. When they fail they turn on a light and/or trigger a relay that we read with a PLC, but they still allow the devices to work. Some of these devices are "mission critical" and cannot be taken off line without consequences. Most of our customers have large lightning/surge/over/under voltage protectors at the service entrance so we only provide point source protection devices.
One of my customers in Florida installed a lightning "umbrella" system. It's a type of lightning rod system, mounted on several towers scattered about the site, and about 100 feet in the air, that bleeds the ground charge into the atmosphere preventing the charge between ground and cloud from building up to the point of a leader forming, thereby triggering an upstroke. They have never been hit by lightning to my knowledge.
