Is there restriction to be registered with more than one professional firm at the same time? Like have an account at Bright and an account at Andover? What if they were both members of the same exchange or both nasd firms? Some firms have software and rates that are good for one type of trading, but have limitations that another firm might not.
There's no restriction unless you are s series 7 registered trader....even then, if you have written conset you can do it