Hi Robert. You may want to double check the AD amplifier after the Pluto. I'm not sure it has enough gain at 2.4G to generate 500mW output from a Pluto. Also, the max output from the Pluto could be lower than +7dBm. The Lime has an even lower output.
Another option would be to use the new version of the SG Labs amplifier which needs 40mW for 20W output.
Better to need a small attenuator, rather than be 4 or 5dB short of signal.
Thanks es GL