I have no direct recommendation for that size, but all I can add is that I use a VST 18g basket (tolerance 17-19g depending on the beans density). I don’t use a specific pressure, I just go by muscle memory, but essentially you’re trying to ensure even density in the puck and consistency between pucks. I think WDT, consistent weight of dry grounds to about 0.2g and a tamp pressure high enough to be sure there are no cavities under the surface is about as far as you can practically take it.
Humidity from day to day makes a profound difference to shot time but in 10 years of being on coffee fora I have never once heard anyone mention hygrometers or barometers.
My coffee yesterday was running 18 >42 in 30″. Today where its damp and rainy, same coffee, same grind, same tamp, took over a minute! So don’t sweat the small stuff.
I prefer a tight fitting tamper, such as my flat base sharp edge 58.5 Goldfinger. I have a convex version too, but the feedback is vague and there are no discernible benefits, so I usually go with the flat.
Hope that helps somewhat.
