Patching Vent Hole in Teardrop

Hello,
We’re working on renovating a trailer we bought and need to patch some old vents.


There used to be a fridge there but we’ve taken it out. The lower vent was an access hatch to reach the controls and things, and the upper vent is just an air vent but is fully sealed in.
We want to put a baggage door there, but the lower hatch is cut in around the fender so we can’t just find a hatch to fit the hole, we need to patch the hole then see about adding a door there after.
Our plan is to get a piece of checkerplate aluminum for the outside and attach it with butyl tape and screws. Then go in from the inside and fill the gaps with spray foam. We’re not sure about the screwing though since the walls are fibreglass and foam. There are some studs, but they don’t line up with where we need to screw in and would really limit the amount of screws we could add. Is the best thing to build a frame around the hole and then screw into that?
Any advice on how to patch with would be appreciated!
Thanks!
We’re working on renovating a trailer we bought and need to patch some old vents.
There used to be a fridge there but we’ve taken it out. The lower vent was an access hatch to reach the controls and things, and the upper vent is just an air vent but is fully sealed in.
We want to put a baggage door there, but the lower hatch is cut in around the fender so we can’t just find a hatch to fit the hole, we need to patch the hole then see about adding a door there after.
Our plan is to get a piece of checkerplate aluminum for the outside and attach it with butyl tape and screws. Then go in from the inside and fill the gaps with spray foam. We’re not sure about the screwing though since the walls are fibreglass and foam. There are some studs, but they don’t line up with where we need to screw in and would really limit the amount of screws we could add. Is the best thing to build a frame around the hole and then screw into that?
Any advice on how to patch with would be appreciated!
Thanks!