They look almost the same size as a truck signal light , go to a truck supply outfit near you and buy a 6" oval light grommet there around $2 see if it fits , if it does you can make a plug out of wood and paintbit black, the grommet will hold it place or if you want to get fancy you can put some clear lights in it a rig it to your dome light for cargo lights

 

I found a big rubber plug about that size in a parking lot once. I wish i had picked it up to see if it would fit

 

its probably there for when the welded the panels in, the robot probably reaches in and welds from the inside

 

Well here is my solution so far. Cut a thin piece if aluminum to fit. (dryer duct since it's strong and can cut it easy). Then JB weld. Tomorrow I'll sand and bedline over it to match the tub. Should be strong enough to last a bit, and I can still remove in the future if needed. Pics of finished job tomorrow. Thanks everyone for the input so far!!!

 

Lol forgot to attach pic.