Deputydog,
RPM is not that important, airspeed is. The tip airspeed of full scale is similar if not a bit higher than on our models. The second blade does not pass through the first blade's vortex at all. The desturbed air is behind the prop before the next blade gets to the same position. The air does not recover until well behind the aircraft. In fact the disturbed air is the cause of P-Factor , a major reason for adding right rudder during take off. This effect is the same if not stronger on full scale aircraft.

Many of you are repeating what I call modeling myth. Some of them are also in full scale aviation such as the down wind effect causing the plane to stall when turning base or final.

Loss of efficiency of multiblade props is due to the added drag of the tips and the prop to hub intersection. There may be other reasons, but passing through the wake or votex is not one of them.

Did you know that one of the reasons turbins can have so many blades is because the tip losses have been eliminated (or almost) by the duct? They are right next to each other yet they never pass through the wake or vortex of the adjacent blade.