Thought I’d provide an update. It looks like my local roaster wins this one.
I started making espressos with the new beans at 18 g, since that’s what the 9Barista folks recommend, and the consensus here seemed to be to go with what the machine folks say. Just for completeness, the basket that I use with the 9Barista is the IMS B652TH27.5M. To complicate things more, I found out that IMS says that this basket has an “average capacity” of 15-17 g. Go figure.
At 18 g and playing around with the grind, I was able to get an espresso that tasted close to what I like, but didn’t seem to have the body that I wanted.
To try to get closer to what I wanted, I started going up on the dose and going coarser on the grind to compensate. I’m still dialing things in, but at this point I’m closer to 19 g, which is my local roaster’s recommendation, than 18 g. I won’t be surprised if I wind up at 19 g.
This has certainly been an interesting experience. It also increases my already considerable faith in my local coffee roaster/shop.