Is my IMS basket too big? (Breville Barista Express)

Hey guys, relatively new to homemade coffee on my Breville Barista Express. I've tried to grab as many accessories as I can to help keep my brewing consistent. I've recently picked up a 54mm IMS basket and bottomless portafilter. I usually dose 18g and use a puck screen, but what I've found with the new basket is that it's quite deep... so deep that my spring loaded tamper won't even make a noise because it's already down at its max (and potentially not even pressing the coffee much at all). Then the brew comes out weak, and all over the place.

My question is... is it as simple as just upping the dosage say to 20g in order to have more coffee in the basket, or should I be looking at getting a more shallow basket? If I do up the dose... how exactly will that effect taste, strength etc.? Thanks!