Sounds good Dave. Been my experaince up to a 21mm is do able. However they can take up a chunk of ones life fine tuning? Prolly depends on who is doing lol. In my case it was myself.
Mines got's after market atomizer,needle, jet etc in it to get it right. Had to find the right size needle for my off ilde progression. Even customized my needle with sand paper ''tiny tiny bit'' chucked up in a drill. Those were good times lol. Dang well worth to me tho. I got power everywhere for the most part now.
My engine does not like to idle for too long or it loads up. So I blip the throttle a tiny bit ever once in a while at the likes of a stop light. Also depends on weather it is the month of july or the dead of winter. Prolly part of this is my altitude.
Think little dragster engine. Those reed velves are part of the equition I am sure no matter what.
My carfully chosen jet was gradually opened up after a hourglass shape. Sounded like a good idea at the time. Runs wicked!
Last wanna say a reeded motor will like a 4 stroke engine type Atomizer too from what I have read.
When I had my little 5.8 hp S6T with the smaller carby/reeds . It would idle all day.
When I had 19's or 21mm on a china girl. They idled just fine. IME
Just what I found.