I'd say not to use the lighting regulator for the MARS simulator. Since the LED lighting board is a constant current board, it's voltage varies dependent on the load. Given that fact, I'd want to use a true constant voltage board for the MARS simulator. I have used this board for the MARS simulator in a number of installs. You can use an LM78Lxx regulator, a good choice is the LM70L08 for 8 volts out. Enough for the MARS simulator board, but not enough voltage to overwhelm it.
Here's the connection diagram.
Here's the BOM for the parts.
Note that C1 is optional, I stick them in as it helps with stability of the regulator if the load is distant from the board. The 22uh choke is for DCS compatibility, if you really don't want to include it, just jumper that position. So, you can really build this with just three parts if you want to go "bare bones".
Here's the schematic for this board.
Here's the Gerber files if you want to make a few and keep them around for similar projects. Just drop this at OSHPark and they'll whack you out three boards for $1.40.
