I purchases the 150 FEQ sander a couple months ago. I have been very pleased with it, however, every now and then I've noticed swirl marks on the material that was sanded. I have tried adjusting the sanding speed when in agressive mode and then go to the less agressive mode with the same grit. Generally, I sand the panel with my drum sander to 150 grit, then use the 150 to take out the drum sander marks. With the 150 FEQ, I start with 150 grit and finish with 180 grit. Any suggestions or tips would be appreciated.