At the time they got swapped, the camper was probably on the ‘00 F350 for ~17,000 miles. Has done ok thus far. Not sure what the definition of significant off-road twisting is but we definitely took it off-road. Regardless, I am biased but I agree with your assessment - I think any serious issues would have revealed themselves by now.
Like money, you can’t have too much solar or battery capacity. Our system has been great but it is possible that we’d get into trouble in very specific circumstances, like the rare event in the summer using the ac overnight followed by overcast but hot days during monsoon season in the SW. Likewise, our diesel heater hasn’t worked right since install so there have been some winter trips where we had to use the minisplit for heat overnight. Even on sunny winter days, solar can’t keep up. Our camping style often involves moving from spot to spot so the DC-DC charger helps but even that had some issues (our prior DC-DC was the older Victron which rarely provided more than 20a. We’ve replaced it with their updated one - hopefully that works more reliably).
I painted myself into a corner by designing the box the way that I did (eg SRW width instead of DRW width) at the beginning. Partly it was because I was starting with a SRW truck and partly an oversight. A 550/5500 chassis is always going to be better, especially if the intent is long, unsupported trips. That isn’t how we travel now or in the foreseeable future so it isn’t a big deal, but I want to highlight the compromises that are always a part of these kinds of decisions.
For longer trips, both the capacity and space from the extra width of the 550 chassis is superior.