Hey Andrew, good piece, got a few comments and questions. I got my set of Dually45s more than 6 years ago, they have no bead shelf/lip, am I seeing right that the new ones do? Also my old Duallys don't think they have the offset drilling like yours either, so to give some extra security I ran narrower tape in the centre to buildup a slight bead lip. It's such a job, that I've actually transferred the rim to different hubs intact and reused the nipples to save re-taping, done it about 3 or 4 times without issue, alu nipples at that.
Can attest to them taking a beating, as you know, tyre pressure can be perfect or not by just a 1/2 PSI with plus, especially depending on the trail. Like you, my riding has progressed immensely recently since I got my new rigid Unit just over a year go and I've smacked tyre to rim a few times when I was first getting going from the FS not realising just how square/big some "small obstacles" I hit without thinking actually were coming off the FS.
I've since basically moved to WTB rims, the asym mostly, because like Vik said, just way too many good options out there now. Just built up a set of Scraper i40 650B wheels to try out, hoping they work as well as the Asym, wish they offered an i40 Asym. I'm actually just going to try a similar setup to you this weekend of 2.6" R/3.0" front to see how it compares to 3.0" F&R, next after that is 2.6" F&R, all on a new set of i35 Asym/Pro4 wheels.
Also have to agree 100% with you on riding a modern rigid, so much fun, so capable, so rewarding. I am riding all of our trails, trails guys have determined require bikes like the FB29, Ripmo, Wreckoning, and while I'm slower on the fast, rough stuff compared, I'm pretty much right there on the steep or chunkier, slow tech. My only problem as I've said before is to find a way to help control the bounce of the front, that's the only thing that deters me from hitting one roll/drop with double hits in it because it's also off camber that goes into a small gully and fear being pinged off because of the bounce.