Got the relays and other components so putting something together to see what is possible.
Will look at using with non CAT controlled radios as well as an SDR RX input.
As move long will post info.
The relays I'll be using at 5V versions...MCB-S-205-C-M basically as have them.
Pretty sure got plenty of some 12V versions as well.
In addition (as will use an Arduino MEGA will look at including an OLED display and possibly a VSWR meter, so don't have to have an extra bit of kit on trips.
One crazy idea is to use a K2 as one TRX and as have a spare K2 enclosure build the SO2R into it, along with the second TRX and anything else might normally require on trips.
Will probably be for CW only and I'll not bother with the mike/phone switching for SSB or data modes.