don't do it.. if you want speed.. p4 render engine is twice as fast. Not sure why.. but if you render the same scene in p4 and then again in p5... it will take almost twice as long to generate shadows. if you tend to only render with a few lights... then it's no big deal. but if you render with some of daz global illumunation sets... over 25 lights... you can add an other 30 seconds to you render if you render in p5 vs. p4...