Compressor cycles on and off

I would be tempted to put another 1/2 pound in and see if it clears up. No bubbles in the sight glass and cool air out of the ducts doesn't necessarily mean it's fully charged. Duct temps can get down to the mid to upper 30's without freeze up. R12 systems can stand more freon before being overcharged. 134 systems will not tolerate overcharging.