Interesting a/c issue on 95 E300, original r134 system

[engatwork]

Just recently went through and put a new compressor/dryer on the listed car. Did the job right but may have overfilled with oil. The issue now is that the belt slippage system drops the compressor out after running a while and the compressor gets hard to turn (working like it is supposed to). I've removed the compressor once and removed some of the oil and it seems to be doing the same thing. When I took the compressor off and spun it by hand I drained the oil and did not have any issue turning it by hand. Can't turn it by hand on the car until after it has sat for awhile. Seems to work ok as long as I am going down the highway too. Drops out at idle. Does this sound like a system that is overfilled with oil? I've got one source that says a little over 4 ounces of oil and another that says 8 ounces total.