hey john up there IMO i think youd be better off using an automotive primer part of the system your using for paint. i reckon powder priming would be too hard, automotive primers are slightly porous so the paint sinks into the pores somewhat helping them adhere (why they recomend you paint over them within the week usually because they close up as it hardens) and i dont reckon this would happen with the powder stuff itd be too hard and they are sprayed electrostatically so i dont think theyd be so easy to key for the paint to stick. incredibly hardy for suspension and undercarriage though but they dont need as much prep as the body to make it straight etc so you can get away with it down there