I could/would do this for taper friendly bands, when I can have the DAT with me, however I am currently looking into getting some sort of Digital Audio Player/Recorder (Neuros, JB3, etc.) for super stealth mode when I need it. The D10ProII is too friggin big for ultra low pro. I would want the hypothetical inline HPF box for these applications. Turns out there is a company here in town that makes all sorts of filters, some of which may be able to be used for my purposes. I'm going to get in touch with them when I get the chance to see if they can do anything for me.