Pot light vapor barrier 'boxes'

gkaro

I all
No luck in the electrical forum so I'll repost here.
I have a project where I'm installing pot lights into 10" joists that are 12"oc.
Need to install complete vapor barrier so the blue plastic boxes are needed. (I've only seen blue)

I cannot find any of these for other than 16"
Do I just stuff them into the smaller cavity?
Slice it in half , overlap and tape together?

Or do they make them for 12" openings?

Thanks

sevenlol

could you possibly add blocking between the joist to make it a 16" X 12" space?

gkaro

The boxes are 16*24. They wouldn't fit.