All four idle mixture screws (under the removeable brass caps) were installed correctly. None of them popped out. Each needle has the required spring, washer, and rubber o-ring on it.
After the carb cleaning, I set each of those four needles at an initial 2 1/2 turn setting. The RPMs were hanging up at that setting. It got worse as I turned the screws in, and better as I brought them out to 3+.
You mentioned the carburetor clamps. I guess it's possible that one of those are loose as I tried not to overtighten them. I will check those out again. How tight should they be exactly?
Also, the pilot needle height is something I did not check when the diaphragms/sliders were out. Is it important to know what height they're at?