As with most things it seems to be more than meets the eye. In searching through datasheets I found a couple of references to signal strength vs LO. It seems there can be to much drive, to little drive, to much signal or to little signal. The circuit response is also affected by coupling components. To test these ideas I did some more spice runs and created over loading and under loading. I will display the results and we can consider them. They all use BAT54 diodes except the last one which uses 1N34A.