On most engines, the idle needle position and high speed needle position are somewhat related. It is possible to get the idle needle closed off so far that you can't get the high speed needle rich enough. Sounds like you are at least "in the ball park" even at 1.5 on the idle needle-just gonna have to have the high speed needle farther out.

I like to set the idle mix so that, at idle speed (2400 or so, depending on the engine and weight of the prop), if the fuel line is pinched closed (use your fingers) the rpm should rise not more than two hundred rpm. More than that means the idle mix is too rich, some engines like less rise. If, when the fuel line is pinched, the engines stops the mix is too lean. Some engines want a lean idle mix, to avoid loading up and/or a too rich mid-range. Also, if the engine quits suddenly when the throttle is opened from idle to full speed, the idle mix is too lean.

I like to set the high speed needle rich enough to get a 300-500 rpm rise when the fuel line is pinched at full throttle. My little Webra 50 on muffler likes Cool Power 15% with Xoar 10x7, turns 14,500 but wants a relatively lean idle mix and also lean high speed mix. Almost too fast in the Kaos arf at 4.9 pounds.

Jim