SkiFreak
Crazy Person
Where do I start?
If you want to know the surface bonding capability of anything, you need to read, or know, the specifications of the product/s you intend to use. There is definitely no "one size fits all" answer to that question.
As @rruff noted, there are a multitude of factors that need to be considered, and without taking all of those into account it is next to impossible to know how much weight any bond would withstand.
You are not buying an "off the shelf" camper. Despite not actually building the box yourself, you have specified many changes to be included by the manufacturer.
Not including reinforcements inside of the panels is simply a failing in project planning. Yes, I know... you don't always know exactly what you may want at the start of a build, but this does not negate the fact that reinforcements could have been included if you had planned ahead. You didn't, so now you just have to use an alternative method.
Having said that, you are not the first person that has wanted to add fixtures to a composite panel.
@Peter_n_Margaret has given one example of a tried and tested method that you could use. There are also numerous other ways you can achieve your goals.
Wow! That's a very open ended question...
If you want to know the surface bonding capability of anything, you need to read, or know, the specifications of the product/s you intend to use. There is definitely no "one size fits all" answer to that question.
As @rruff noted, there are a multitude of factors that need to be considered, and without taking all of those into account it is next to impossible to know how much weight any bond would withstand.
Correct me if I am wrong here, but as I see it, you are a DIY builder.
You are not buying an "off the shelf" camper. Despite not actually building the box yourself, you have specified many changes to be included by the manufacturer.
Not including reinforcements inside of the panels is simply a failing in project planning. Yes, I know... you don't always know exactly what you may want at the start of a build, but this does not negate the fact that reinforcements could have been included if you had planned ahead. You didn't, so now you just have to use an alternative method.
Having said that, you are not the first person that has wanted to add fixtures to a composite panel.
@Peter_n_Margaret has given one example of a tried and tested method that you could use. There are also numerous other ways you can achieve your goals.
As many others have done for decades.
