. Some relays have an internally configured suppression diode. Since you will be firing the coil from a reversed polarity standpoint from which it was designed, the suppression diode wont do it’s job. (if it is so equipped)and will short circuit. Using a non suppressed relay will allow doing this.
The diode is there to prevent flyback voltage from making its way back to the control unit. You could easily add suppression diodes to the bar itself in the required polarity.
Google “suppression diode in relay” for more detail on why/ what/ how.
I found out about these things the hard way last year when wiring my coupe. After years of using relays that had no polarity preference, somehow I ended up with some of these diode relays. My fuel pumps didn't work because the polarity was backwards. Reverse polarity instantly burns up the relay. I burned up up about 3 relays before I figured it out. Beware of the diode relay!
