Mike, you changed the rules to attempt to make the challenge more like the actual competition. A good idea I would say.
If you want this to be as real and comparable as possible to the actual competition...you should plug.
You can shoot a 225 that will plug a 225...and you can shoot a 225 that will plug a 235. There is a potentially massive difference in the outcome. I actually had a 230 card that plugged a 243.
You would then have parity among the different calibers...which is the purpose of the plug anyway.
Plugs are not expensive items...and they should be a part of every competitors tool box.
Just my opinion of course.
Mike