I don't know if it is safe to run a modified Bradley without a PID. I've always used some type of temperature controller when running two 500 watts. There are at least a few on this forum that are running 1000w or 900w without a PID. I have the old original Bradley. Besides the issue of the Bradley controller handling the extra load I mainly use my third party temperature controller as an extra insurance to prevent the cabinet from getting too hot, and possibly causing a fire.