Sorry chaps but the leaning out of a pumped petrol engine carburettor "once it unloads" is hogwash. This is glow engine thinking and it does NOT apply to a petrol engine.
Rich running engines are not more reliable than a slighly lean engine. It may run a few degrees cooler. If there petrol, air and spark it will fire....simple as that.
Lastly how in heck is gaining altitude in flight it going to change the mixture significantly? Air is a lot less dense than water so it does not change barometric pressure significantly every 10m altitude gained.
tuning these things is so simple. allow for 30sec to warm up and open up to WOT and set the high speed needle for peak rpm.
Then ease back on the throttle till its starts to pop and miss (4 stroke) and lean the LOW sped needle till it goes away, then ease back on the throotle again till the next 4 stroking point is reached and lean the LSN again till it stops. repeat till you get to idle. Check for transition through the rev range and anywhere it feels lean, richen back up a little, or if it still 4stroke, lean further. Work you way back up to WOT and then again ease back on the thottle. If no 4 stroking occurs then its good to go but its likely it will still have a spot somewhere in the rev range where it will briefly 4 stroke.
forget your glow engine thinking with petrol engines.