Convert a Porter-Cable 42690 edge guide into a micro-precision router compass

I needed a circle-cutting router guide to cut the recess for the rosette in my soundboard. At first I tried the compass that came with my Rotozip, but it was too floppy. Next, I built a compass for the Dremel router base edge guide, but the depth control was unreliable. I considered buying the Jasper 400 Circle Cutting Jig, but after looking at the design for this compass jig, I decided to convert my Porter-Cable router edge guide into a compass jig by replacing the removable edge guide with a flat plate. Using the edge guide as a template, I traced the outline onto and cut the plate out of 1/8" hardboard, then drilled matching holes. I also drilled a 1/8" hole on the opposite end for the center pin. I reassembled the guide and attached it to the router. To mount the router flush to the plate, you have to remove the plastic base plate on the router. Once mounted, I extended the arm to cut the slot, but it turned out sloppy. The pin/nail must sit flush with the top of the guide plate and there shouldn't be any slop in center hole as it rotates around the pin. I am considering to remake the plate with 1/8" aluminum, but it's not necessary.