Learning a new way of doing things in the workshop doesn't necessarily irritate me. I actually think that learning new things and setting up processes in the workshop is rather fun. However, I think that I did cuss a few days ago when a piece of lumber split when not expected - argh!!
I started using the small jasper circle cutter the other day, cut one recess perfectly, 6.5" dia. Then did it again same way for the other baffle, it was 1/32" too small, driver wouldn't fit. Thankfully, no shortage of wood at HD. I need more practice.
Yep, I have been there and done that a few times. The following snippets may help.
1. Make sure the center guide pin is quite snug in the hole. I cut several 3/4" pieces of nails that are just large enough to fit through the Jasper Jig holes and use these nails for guide pins.
2. Adjusting the router up & down between cuts will often cause the position of the bit to move very slightly - perhaps 1/32nd of an inch.
3. Always, Always, Always accomplish a perfect recess on scrap lumber before cutting a recess on the good stuff. There are no adjustments between these cuts.
4. Ensure the pressure on the router is always the same. I generally push gently away from the guide pin.
5. On the rare occasion that the recess remains slightly too small, shave/remove some of the aluminum driver flange with a belt sander. This is darn easy. Then, use a good black magic marker to restore the color to the driver edge. Nobody will see the driver edge since it's concealed in the baffle.
Hopefully some of this helps.
Dave