Hmmm I thought the R600 was used as an auxillary cooler. You basically use a large R600 charge to max out the heat-dissipation abilities of your condenser and then evaporate off the R600 in an HX with the rest of the Autocascade charge, dropping it down below room temperature. Can't imagine R600 condensing before the condenser like you say and evaporating in the 200psi atmosphere of the highside with decent temps, but I'm no professional.