Hey not trying to break your balls here, but sometimes the spout doest divide the yield exactly. I reckon you should try to fit both cups on the scale for a more precise measurement
I have the same machine as well as a df64 v4. What grind setting do you use? I've been trying to dial in with 18g, do you think I'm under-dosing? My shots are sour and I tried going finer but then it nearly chokes the machine. Not sure if I need to be very precise with the grind settings
The portafilter for BDB is 58mm, I find dosing around 20-21.5g works for me. The grind size really depends on the beans, but my usual grind size is between 8-12 on DF64.