You assessed what I (and many others) do with a new engine correctly. When it makes it to the nose of the plane it gets the needles set for max performance from the first run. As a rule I don't bench run any gasser. That first run is the one that sets things up for the rest of it's life, which is usually quite long unless it hits the ground. I know of at least one major university applied physics lab that recommended the same thing in the running of engines on other forms of air vehicles with smaller engines.

Let's move away from needle clock positions since it's really not relevant and do some rough needle settings. Start the engine and lean the low needle until it drops rpm. Back it out to peak again. Turn the high needle until max rpm and back off about 100 rpm. You don't need a tach, your ear will do fine. Check the transition from low to high. Go back and re-peak the low needle. Leave it at peak. Once again peak the high needle and back off just a touch. Check transition. Always leave the high needle just rich of peak, and the low right at peak. Amazing how often someone will be tweaking the high needle when it's the low needle that needs to move about 1/16 turn to balance it all out.

Remember to do all this in short running sessions on the ground, 3 to 4 minutes, or less, if possible, leaving about 1/2 hour between runs to let the engine cool. No cowl!! 150c (302f) is as high as you ever want to get with the engine temp. Those little heat guns are terribly inaccurate, but better than nothing. If you use one always aim it at the base of the spark plug for a reference location.

Back to the needles. You should be very close at this point. Close enough to get some pretty nice flying in withut concerns about the engine. It may need some minor adjustments from this point as it breaks in. Use the oil you intend to run forever from the first day unless the manufacturer is anal about a break in oil. I prefer synthetics for their superior lubricating properties, but some manufacturers are still locked in the stone age and like nautural oils. To me the purpose of oil is to lubricate, cool. clean, and minimize wear. Why would I ever want to maximize wear with a lesser quality of oil? You wouldn't run Quaker State in a 425 kitty, would you?

Edit below;

I forgot to note that 95% of transition adjustments will be made at the low needle, about 1/16 of a turn at a time either way.

For those just getting their first gasser, note that the needle settings are much finer than those of a glow engine. Where you used to be able to adjust things in increments of 1/2 turn or so you will find gassers are much more sensitive and require all the needle adjustments to be done in finer steps. A 1/8 to 1/16 of a turn can be quite a difference.