That's only a 389 in those pics mashinator, not a 1530. I had too many hull splits and deflection in my previous boats to not even consider 3mm alloy again, BUT, I drive my boats
hard, basically full throttle everywhere up until anout 15 knots of wind where I button off - most people are content to cruise at say 4000rpm, but I enjoy going quick in the rough, this has a toll on alloy hulls though and I'm 100% positive if I had gone the 3mm hull I would have deflection around the ribs by now. I think for most people 3mm would be fine, but Wellington conditions can get pretty hairy at times as some of you know and the last thing I want to be stuck with is a hull split 5kms out into Cook Strait - (not that it would really matter much with a pontoon with 3-5 air chambers, but I'm fussy on a quality, lasting product).
I also think the extra weight improves the ride as John says, it is NOTICEABLY quieter skipping across the chop in a 4mm hull vs 3mm hull (the sound is a dull thud, thud, thud skipping chop... not a loud twang, twang, twang!), the 3mm reasonates far more, but the 4mm keel strip I also had added would also help this again - Brendan did an amazing job of fabricating my hull with the keep strip - it's seamless - 8mm of alloy is soooooo damn strong, and a really hard welding job to do on such thin plate with such curvatures.
Also the extra security of 4mm hull plate resting on trailer rollers is a plus for me when towing (some places I fish are down semi-4WD tracks). I really think for such a small amount of money it's a worthy 'peice-of-mind upgrade as was the full length keel strip - it makes the boat extremely stiff and safe in the knowledge if I do konk a log at 30 knots I'll be fine.
The stabi 1530 is a larger boat than the Frewza and has far more floor space, the Frewza is only 4.1m not 4.4m. I still think the Kiwikraft 440 and 460 are the kings of the 4.5m plus class. Daveo can tell you about the Senator as well, a very nice hull, not as many around as the competition, but ticks many of the boxes (just won't fit in your garage Ritchy!)... Interestingly there seems to be a big difference IMO between the interior size in a 4.4m boat vs a 4.1m boat.
I'm intrigued by the DNA, anyone got some pics other than stock pics?... I need a new project!