Progress continues with getting the K3 TWIN setup working. I have posted all the details on the Elecraft reflector but here is a cut and paste of it:
I have the Elecraft "TWIN" setup working with the Microbit control and 
remote boxes. The instructions in the Micorbit RRC-1258 MII manual are 
pretty good. The URL is 
www.remoterig.com. The one thing that is not 
clear IMHO is the last line of the setup for the K3 TWIN:
COM2 Mode listed as Logical Parallel with COM0 is not in the radio 
settings but are in the Serial settings and are for both the control and 
remote(radio) boxes.
It is also not mentioned that USB used as COM0 should be YES under the 
Control Radio Settings and USB used as COM1 and USB used as COM2 should 
be NO.
One thing I missed without going over things a second time is that the 
cable between the Control box COM2 and the K3 CAT is a cross over. The 
cable between the remote box COM2 and the K3 CAT on the remote K3 is a 
straight cable.
The Microbit documentation never talks about the information from 
Elecraft on getting in and out of the TERM mode. This was necessary for 
me to get things working. Once it is running then it happens 
automatically unless you get out of TERM and back to NORM.
You need the cables as describe in the Microbit documentation.
It is very impressive and works "SUPER" and makes remoting over the 
Internet or over LAN a breeze once you get by some lack of documentation.
For logging/control one can use say COM1 from your computer and a serial 
cable to COM1 on the Control Microbit box. These settings are discussed 
under Logging or computer control, RTTY etc. in the Microbit manual but 
IMHO they are not complete. If you want to use a serial cable between 
your computer for logging and control and use say COM 1 out of your 
computer. Set your logging control program to the same in this case COM1 
and be sure the baud rate is the same everyplace. You still leave USB to 
COM0 as YES. Be sure to do what the Micorbit manual says in regards to 
the mode 7 settings.
If you want to use your USB cable to the RCC control unit for 
logging/control and not have a serial cable then you have to set USB to 
COM0 to NO and set USB to COM1 to YES and set your logging/control for 
the virtual COM port that your computer has for COM 1 if that is what 
you are using.
REMEMBER TO APPLY YOUR SETTINGS and not just SUBMIT!!!
If you want to control a K3 remotely using the Microbit boxes, ie not 
use two K3's but just the remote one I have documented that in the 
Microbit forum and how to control one rotor and do CW. I have RTTY to do 
yet and control of rotors and antenna switching outside the Microbit 
boxes. You can do virtually everything with TXR manager in regards to 
controlling the K3.
The "TWIN set up is very nice but you have to spend the money for a 
second K3. This makes the prospect of a K3 (0)with no RF that Eric 
mentioned very interesting! It would be nice to have something less 
valuable and smaller to carry with you and most things are a bit easier 
to do on the control radio although there are a few things on TRX 
manager that are IMHO easier than the radio such as band changes.  I 
need to do a lot more before I form much of an opinion on way or the 
other. Obviously the "TWIN" set us is the easiest!
It is possibly I made an error someplace in this information but I have 
tried to be very careful. Anyway I do have it working all OK and it is 
impressive so it can be done. It is just a matter of getting the correct 
settings.  What you can do with remoting has got to be a very big deal 
over the upcoming months as it is rapidly getting a lot easier to do. It 
is very real solution to problems a lot of hams have with noise of all 
kinds, RFI, lack of antennas, restrictions, on the road a lot, needing 
to be at different locations and the list goes on, the hassle of taking 
a radio various places; especially if there will be a K3 (O) or you can 
do it without the "TWINS".
Ed W0SD