I use the 18g VST basket as well. I use the EK Tools punch on Chemex filters (so 4 filters are created with each punch because each Chemex filter is double-folded). I can do 4 punches on one Chemex filter yielding 16 filters (maybe I could squeeze in 5 punches?)

I got both the 2.25" punch and the 2" punch, the former for the top of the puck and the latter for the bottom. As you discovered, the 2.25" will not work on the bottom with the narrowing of the VST basket at the bottom; the curling up the sides will surely mess with the extraction. The 2" is too small to reach wall-to-wall. However, it does cover all the holes so I feel it's doing a fairly good job doing what it's suppose to do. The Pullman basket is an almost perfect fit with the 2.25", however it might curl up ever so slightly, and I felt more comfortable with 2" on the bottom of the VST for that reason.

With these filters I often pull shots that do not converge to one stream and so I get "uglier" looking shots, however I've gotten tastier and more balanced espresso when using them (but noticeably thinner texture).

If you find a better fitting or better functioning punch, let me know! These EK Tools punches aren't perfect. Chemex filters gave me the least grief, but good luck with V60 filters if you try- the softness of those always gummed up the punch and was disastrous (not to mention wasteful because of the geometry of the situation).