Well, I'm basing my idea on an old post I saw on dbstalk when discussing a Tivo THR22 (but the poster expanded the comment to include any RS-232 capable machine)...Here is the post for reference:

Additionally just wanted to comment in using more than 6 rs232 on the MSC-400. You can use multiple devices on 1 rs232 port on the MSC-400. You can use a "y" splitter but it must be a 4 connector "y" splitter which is hard to find. It's easier if you make your own rs232 cables for your msc-400. The caveats are as follows: all devices on the single port need to use the same settings such as baud/parity/stop bits for all devices you will share with that port. Additionally, you cannot put two of the same device on each port such as directv receivers. They have to have different serial commands. Much like IR when you send a command to the device, it will ignore it if it doesn't recognize the command. I use my serial port 7 for my 4x4 hdmi monoprice switch. And port 8 is used for a 4x2 hdmi monoprice switch. They both have identical serial commands so they can't share a port with each other. I also have a thr22 on ports 7 & 8 shared with the hdmi switches. The thr22's both use identical commands as well so they can't share a port. But since the commands are different from the hdmi switch they can share a port since the baud settings are identical. When a command is sent on port 7 for the hdmi switch it is sent to both the switch and the thr22 but the thr22 ignores it since it isn't a valid command for it. However the switch accepts the same command received but accepts it as a recognized command.

...so the question is, is the Y splitter I linked to in my original post the kind that he is talking about there with "4 connector"...anybody able to help me on that?