Fireboy MA2 automatic/manual system. First serious upgrade I made to the boat. As well as the antique original Halon system. Upgraded due to the obsolescence of the Halon system - manufacturer long since out of business - disarmed the scary control system - if it works, it will be via the bi-metal link at the bottle head and be additive to the MA2.
I followed the Fireboy guidance for sizing the system, then doubled everything. I do not have WT compartments, so I assumed that much of the suppressant volume would be lost (dissipated) through the bilge. I suspect that many systems out there are undersized because people forget that most plastic boats, while having "engine rooms", don't have the ability to effectively isolate the space. Not sure my X2 approach is actually enough. Hope I don't ever have to find out.
Interestingly, I bought the system from a "Taiwan Trawler" parts outfit in SoCal at about 50% of the Fireboy-Xintex quote through its dealers. Guess they had an extra and I got lucky, but another case where serious research paid off.