They always run different with the cowl on. And then it runs different once you take off and start flying.

Tune it on the ground with the cowl ON. Go fly it and see how it sounds.

I tweak the needles with the engine running if I can. Not possible on some engines though because the carb is on the side and angled so the needles are facing the prop. I'm not about to stick my hand in there with a tiny screwdriver. Just shut it down and make a quick adjustment, then start it up again.

On your DA--adjust it running through a small hole in the cowl. Some guys have come up with very slick screwdrivers to slip through the cowl and adjust while it's running. A standard screwdriver is hard to keep from slipping off the mixture screws while it's runing and shaking. Guys will put a little piece of fuel tubing over the end of the needle and leave it hanging out a bit. Then, when you slip the screwdriver in there, the fuel tubing holds the screwdriver on the needle.

OR:
Some guys will cut the head off a popular size allen head bolt. (4-40 or 6-32) Remove the needles from the engine and have the allen head bolt brazed or welded onto the needle. Then you can use a long ball driver to make your adjustments.

Use a tach. Your new to this and if you don't have a good ear for tuning, you'll fight it forever. Lean the high side to peak and back it up a little. Then lean the low end and see how it keeps getting better and beter at transition. Eventually, you'll end up leaning the low end too far and it won't transition. Just back the low end screw out again so it transitions perfect. Now richen it up the thickness of the slot in the adjustment screw. That should knock your idle down about 200RPM. Go fly it for 5 gallons. You'll still have to make monir adjustments to the high speed needle on very cold days or very hot days, so don't get the idea your done adjusting needles. You DO have to tweak it sometimes. I check my engines every day. Adjust the high end once in the morning and then fly all day. Doesn't usually need adjustment, but I check it anyway. Most I've ever had to adjust it was about 1/16th turn.

Gas needles don't react to adjustments as quickly as a glow engine. On a glow engine every click of the needle gives an instant response. On a gas engine--better to make a small adjustment and wait 5 or 10 seconds for the settings to take effect.

Patience.