I've just installed the Namco System 1 Multi and it is working great so far; I'm missing a SEEQ chip for now so I've got one ordered before trying the full list of games.
However here's a precautionary tale: If you remove the dipswitch block for whatever reason, make sure you reinstall it over all of the pins; the shroud around the pins on the multi allows you to install the dipswitches to the left or right by one pair of pins. When I did that, I got nothing but a black screen when I powered on. Thankfully all I did was try pressing the boards together before I spotted what I had done. I nearly ended up taking the boards apart, removing the multi and reinstalling all of the original chips to troubleshoot.
However here's a precautionary tale: If you remove the dipswitch block for whatever reason, make sure you reinstall it over all of the pins; the shroud around the pins on the multi allows you to install the dipswitches to the left or right by one pair of pins. When I did that, I got nothing but a black screen when I powered on. Thankfully all I did was try pressing the boards together before I spotted what I had done. I nearly ended up taking the boards apart, removing the multi and reinstalling all of the original chips to troubleshoot.