I have done this type distillation with 30/60 petroleum ether and have gotten good yields. I reduced approximately 140 ml down to 35 ml. BP of the PE I was using was about 47 degrees C according to a type K thermocouple directly in contact with the PE as it boiled in a flask. This would imply that the PE had primarily the neohexane isomer which boils around 49 deg C.
Everything mentioned herein has been deemed by our staff of expert psychiatrists to be the delusional rantings of a madman who has been treated with Thorazine who is hospitalized within the confines of our locked facility. This patient sometimes requires the application of 6 point leather restraints and electrodes at the temples to break his delusions. Therefore, take everything mentioned above with a grain of salt...