Lean idle. Rich cruise.

it's possible to shorten the slot itselfs
Note that secondary side are usually higher up but not always.

This guy went on a journey from greenhorn to a carby smarty. :)
https://www.tapatalk.com/groups/racingfuelsystems/transfer-slot-lengths-t1285.html#p11866
https://www.tapatalk.com/groups/rac...eas-and-why-the-differences-t1737.html#p16849
https://www.tapatalk.com/groups/racingfuelsystems/making-throttle-slots-smaller-t1600.html#p15566

And a great thread with for anyone who wants to go through it.
https://www.tapatalk.com/groups/rac...-slot-length-difference-t1402-s30.html#p13272