sp300b just ended conversation over the phone with mehe'll obviously (restless spirit ! ) try lowering source resistor of lower SS .....anyway - what he tried - now we have dilemma what's more influental in his test - change in overall (sum) value of these two resistors in middle of totem pole , or change in their ratiogenerg ( and all ) - be careful when decreasing voltage for optocoupler ( led part) - you can shut off that LED , and circ will be still biased fine , but you will loose current tracking , for which optocoupler is put there , in first place