Today I duplicated my DC-DC Step Down Buck Converter to my Spare Ramps 1.6 board. I am now powering both ramps with 24volt power supplies.

Have not ordered a pair of Full Graphics controllers for my newly purchased Arduino Mega 2560 R3's and Ramps.
Though it is still on my list of parts to be ordered.

My next modification will be to remove the AMS1117-5.0 regulator on the Arduino and replace it with this same DC-DC Step Down Buck Converter. This time instead of setting it to a variable voltage will be using the set 5 volt jumper pin on the converter.

This will allow for the additional power requirements needed to operate the Full Graphics controller I will be using. All power supplied from a single 24vdc power source from the Ramps 1.6 controller power pins...