Port side flagpole holder

[DMil26SD]

I have 2012 26SD. The two bolts that secure the flagpole holder on the port side keep loosening. I can barely hold the nut on the forward bolt through the vent grill. The one in the rear is not accessible. I have tried to gain access from the engine compartment but there is a board blocking the way and I see no way to remove it. So I was wondering if anyone knows how to remove the vent grill on the port side.

[Titaniumboy]

Can you post pictures of the vent grill and the board blocking your way?