If the engine ran better on the ground than it did in the air, you may have an air pressure issue in the cowl causing the regulator part of the carb to richen the engine in flight. Make sure you have plenty of air exit area in the cowl and you may benefit by adding a baffle in the front of the cowl to restrict the airflow to just the area in front of the cylinder. Large round cowls are known to cause rough running if not baffled in this way. In some cases it may be necessary to install an equalizer line from the regulator cover back into the fuselage where air pressures are more stable. These are many times connected to a pill bottle or balsa box with a tiny hole to limit the effects of air pressure changes. Much has been written about this so do some searches and you should find way more info than you may want to know.

You may benefit by checking the engine's timing. The sticky at the top of this page disussing Rcexl ignition sensors has quite a bit of content about timing. You can learn quite a bit from that thread. There are many other threads that also discuss timing. Your engine uses the RCexl igntion so any thread discussing timing and that igntion will apply to your 30.

I dislike adding extensions to gas carburetor needle valves! The extensions can vibrate which can cause the needle valve to wear the carb body threads over time .... then you won't be able to keep a needle setting. Unlike glo engines, gas carbs are pretty much a set and forget thing so once you get past the inconvenience of setting the needle valve early on, once set you won't have to mess with them much if at all for a long time to come.