Dante,
I looked at the MIDI implementation chart for the MS-3. It actually does not recognize most MIDI commands. Almost everything in the column has an "X" all the way down the list. The only CC commands it does recognize are from what you have connected into the expression pedal and the footswitch plugs.
The really weird thing is the SYSEX is not available to the public. I've never seen that in any MIDI device before. The SYSEX chart tells you what commands can be sent and received, and what channels to assign them to. MIDI works on a handshake principle, and both devices need to complete the handshake.
I think for MIDI, you'd be better off plugging your MIDI controller into the Grandmeister and running a MIDI cable from that to the Switchbalde from the MIDI Thru jack. This way the command is sent to both amps at the same time. The other alternative is to send MIDI to the Grandmeister, then have the Grandmeister send an independent different command from the MIDI Out jack to the Switchblade. It's sort of like midi mapping in a different way, and that is only IF the amps can be programmed to do that. They have to all be on the same channel for that to work which means that if one of them is in Omni mode, it needs to be set to mono mode and on the same channel. Many MIDI devices don't respond in Omni mode.