I have built both the K0LR circuit and the Ultimate U3S. And they are both transmitting now the ID "FL". The K0LR circuit is on a protoboard now and transmits "FL" in slow speed CW and is connected to a dipole cut for 22 meters in the attic. I have the K1EL chip programmed for the CW ID. The circuit I built is very close to the K0LR schematic with only minor changes, but just as simple.
The Ultimate U3S is much more time consuming to build but has many more options. It is feeding a another dipole, also in my attic, sending "FL" in FSKCW4.
The transmitted signals are about 0.5 Hz apart.
Dave