As an experiment, with the Chatswood, try the spouted portfailter, 19g dose, 38g out and see if you can consistently get 30-32 seconds.
It’s also one of my favourite espresso blends and having extracted probably 5-7kg of it, I find 30-32 seconds at 95 degrees is the sweet spot. Less than 28 seconds and it’s almost undrinkable. More than 35 and it starts to get bitter very quickly. As a note, I never adjusted the boiler temp or steam boiler temp the whole time I owned it.
The spouted filter should help mask a few prep inconsistencies and will be way more forgiving. If you can get a consistent 30 sec shot with spouted, you can assume more consistent prep (WDT/tamping) will be causing some of the frustrations with the bottomless.
I’m using a flat burr grinder vs your conical niche but beyond that I can’t see why you shouldn’t be able to get consistent 30 second shots with Chatswood.