I just realized I have written about it in other places, but not here. Following up on the topic.
TL;DR: Surprisingly durable outdoors, no broken parts despite a bunch of hard landings. Shakes and deforms but survives about 10 mph gusts.
This bit is all about flying the Kaiju outdoor, not my indoor practices.
In my lovely inland location highly variable conditions are the norm. Wind forecasts may say 5G15, and in the field wind varies from a breath's force to decent speeds from moment to moment.
Often I find myself setting up a Kaiju on 40' lines as a backup plan when winds calm down and I can't keep other kites up. Often I fly the Kaiju ten minutes at a time, or friends flying it for ten or twenty minutes, then returning to other kites. Sometimes an entire hour or more may go by drifting around on the Kaiju. I'd estimate around 10 hours of flight this way since writing the question a year ago.
Over the past year I've found it can handle a decent gust, probably around 10mph, but it shakes and shudders and deforms as I race to the edge of the wind window. I've had a few hard crashes, and I've also handed the kites over to beginners once I was confident in the kite's ability to handle it. (I know one beginner, a neighbor, bought their own Kaiju after trying mine.) So far hard crashes have knocked spreader spars from their fittings, and also popped standoffs completely out but they could be reassembled without damage. Attempts at slackline tricks have generally pulled the spreader bars from their fittings, although that could easily be due to my relative novice skills at the tricks.
There have been several times (mostly when others have flown it) when I was certain I'd be replacing a spar, but have been pleasantly surprised that all it required was hunting for a spreader bar that had bent under tension and flung itself from the kite under a bend rather than snapped. They've always sprung back to normal. I've watched spreader bars fling themselves quite some distance from the kite but still not break.
If the wind is strong enough for another kite I'll fly them instead. On light wind days I'll set up the full sail Djinn and Kaiju both on 40' lines, other times I'll set up one of the dual lines (Hydra, Kymera, ZigZag, or Quantum) for practice with the Kaiju as a backup. When the bigger kites won't stay up, I can get a Kaiju in the air to pass the time.
It is sensitive and doesn't handle large input well, without pulling a spreader. It is very relaxing, I can fly one handed with lines looped around pinkie and pointer fingers, and still make comfortable twists and turns in the air with my wrist alone. It doesn't handle much more than gentle twists and turns, but at least it is airborne.
It is very rare that I can't get the Kaiju on 40' to stay aloft. People I'm with also usually have no trouble with it. On the rare occasion I find myself falling back to indoor skills on those lines, or find my flying partners struggling to stay aloft, it's usually not worth the time at the park, time to pack up and do house work.