I had some problems with the engine bay fire system from Mac so I would not trust the system he sells.
Mine was consistently loosing its' charge. 5 times is pretty excessive over 3 years. The last time it was inspected, serviced and charged by Mac's assistant and it still didn't hold a charge.
BUT, the bigger problem was actually getting it recharged. I had 2 shops refuse to service and charge the bottle because it had a Halon gauge, which was not correct for the content. They both just handed it back to me. One of the shops that charged it, would only do it with air pressure and would not tag the extinguisher, with their name as being serviced. The didn't even charge me as they didn't want their name attached to the extinguisher with a receipt (probably had an experience with a lawyer at some point)
One shop actually inspected the unit and suggested I return to the company I purchased it from, as it didn't have the proper valve and labeling.
Note that the shops that wouldn't service the unit were in California and Oregon so it wasn't a "local" issue.
I do however think Mac's liquid fir suppression system is the way to go and I do carry his small units in the motorhome and the car.