You are pulling 20% EY average shots on the monolith conical. Your coffee is far from light roasts, sorry to say but light starts at 90 agtron, your beans are 71, that is like an espresso roast. The beans are to inflated to be roasted light, you can post some pictures.
Because you are limited with none or less preinfusion you tend to under extract in the 1:2 ratio. A lot more remains inside the coffee puck and that is shown by the 1:3 ratio that lowers the strength but adds more EY%, because there is more to offer left there.
I bet with a longer preinfusion using the same coffee and the same grinder you could pull easily 22% in a 1:2 ratio.
Use an IMS or a VST basket with 20g coffee, this will end in less channeling and more even shots. The VST 17g basket I have but its not plain straight on the walls at the base of is basket. The 20g VST I find it better and less channeling, easier to work with.
If that is the coffee you are using and you like that is great, and I am happy that woks for you. My advice would be to not be tempted to go into big expensive flats because you won't obtain better tasting shots using a different grinder. The sweet spot for those kinds of roasts are where you are 19-22 EY. Adding more EY and going rampage on 70 sec shots will just bring out the darkness out of those beans.
We went to big flat grinders to find a solution for really light roasts, that could not offer any good result on normal grinders.
Here is a picture of a light roast, it is a bit exaggerated but just to be clear. I respect and won't debate other choices about drinking dark-medium-light roasts.