I just hit 800 miles on my RADmini this morning! WOO!
I am not sure as I am just getting back into biking using this as both my commuter vehicle and recreational fun. However I have noticed as far as "performance per watt" (just intuitive observation) that if you step down your PAS to PAS 2 and pedal harder I've been able to hit 23mph consistently and every once in a while 24mph. Of course down hill you can get going quite fast. There is a hill in my area I was going almost 40mph! Kind of freaked me out so was slowly edging the brakes.
Any rate the controller for the RADmini sets the rules to abide bike lane laws in the majority of states which is limited to 20mph. If you haven't noticed already it stops feeding power once you exceed 20mph (I remember a trick in the King Meter settings to get it to roughly 22mph before it cuts out, it's in this forum thread somewhere).
If you find a chain ring to upgrade to perhaps let us know! I have considered swapping the controller out for something that is "dumb" and would just let me power the motor as much as I want to instead of governing at 20mph.
@brrrett you should also try taking challenging grassy or dirt trail hills. This bike makes me feel like a champ and is really does so well up hills. I weigh 180 and can hit 15mph steady with just throttle however I dont do that because I like to feel a little burn. Hope this helps some at least for your new mini.