Some in this Hackaday post have voiced their concerns about voltage isolation on the Reflowduino Pro and said that they would feel better if there were more physical isolation between the relay output pads, such as a slot or cutout. Although the Reflowduino does meet the IPC-2221 spacing guidelines, I thought this might be a good idea!
I just updated the Reflowduino to version 2.1 by adding a cutout in between the two relay output pads. I have uploaded these latest EAGLE files on Github.
Thanks for everyone's input, and as always, feel free to comment and suggest!