inverter broke free from mount

[JRK]

On the drive home from delivery, I noticed that the Oliver rear light was being intermittent. At a forum suggestion, I checked the buss bars beneath the small dinette seat for a loose wire, and found that the inverter had broken loose from its mount. Only the top two screws had been installed. The bottom two screws had not been placed (or there were no screw holes in the mounting plate indicating that). The inverter was able to flop about in the compartment, banging into the circuit breaker and bouncing on the buss bar. The intermittent problem probably has been identified.

The mounting plate was plastic - probably resin? The plastic plate is glued or affixed to the interior, inside seat wall. I would prefer to put a bolt through the mounting plate with a fender washer or similar on the back, but do not see how I would be able to do that. One screw stripped out, probably after the stress from the other screw caused the fracture - or the other way round.

My question is suggestions on how to best replace and mount the inverter. If all four screws are in place, it probably would stay put. The recommendation was for #8x1/2" screws.

Thanks, 

John