Side popout "drawers" for feet (bed extension)

While trying to figure a way to get my 6'1 body in a not too heavy trailer, i came up with the idea of having a side pop-out hollow "drawer" to add a bit of width to the trailer, where my feet would go when sleeping.
I was wondering if anybody ever tried something like that and whether it was a bad idea, don't see why it would be bad except maybe it would be hard to prevent water/rain to get in at the "drawer" seal ?
Here is a quick shema :
So when popped out (hollow) it is the "end" of the bed (feet), and when popped back in it could maybe serve as one of the dinette bench.
I would probably use heavy duty rails to make it slide in and out (the kind of heavy duty rails they use for servers in data center)
Anyway, was wondering what other thought about that idea.
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I was wondering if anybody ever tried something like that and whether it was a bad idea, don't see why it would be bad except maybe it would be hard to prevent water/rain to get in at the "drawer" seal ?
Here is a quick shema :

So when popped out (hollow) it is the "end" of the bed (feet), and when popped back in it could maybe serve as one of the dinette bench.
I would probably use heavy duty rails to make it slide in and out (the kind of heavy duty rails they use for servers in data center)
Anyway, was wondering what other thought about that idea.
[/img]