I know it's late, but I am answering in case someone needs help in the future.
Hey, thanks for posting that bit of info. My devices are daisy chained, not independently attached, but if they were, I would have went into the Windows midi mapper each time I needed to switch which device DosBox should be using which is a bit of a pain. Changing one number in the DosBox config file is easier for me and does not affect which device Windows itself is set for.