Simple Sleeping Platform w/ Bedslide Help

Hey Everyone,
I'm new to the forum, so if i'm posting this in the wrong place please just let me know and i'll move it - I looked around and couldn't figure out if there was a more appropriate place.

Ok - I have been scouring the web looking at sleeping platforms and could really just use some personalized help since i have one added aspect that I, to my amazement, cannot find anyone else who has tried to do the same thing!

I hitting the road with my girlfriend and trying to come up with a super simple sleeping platform, quick. Heres the rub - I have a bedslide installed in the truck, and I am thinking i'd like to leave it in there rather than deal with taking it out and storing it somewhere (I love the thing and don't really want to get rid of it, and im homeless now, so storing it is unnappealing). This sleeping platform is genius, and i'd like to do something really similar, except I don't have the "factory notches" that he's talking about.

So i'd like two (or however many really) separate pieces that can be taken out like that platform, and I want the bedslide to stay underneath, which means I can't have any support running down to the bottom of the truck bed like in other platforms (except on the sides around the bedslide. Also I have a standard cap on, and with the bedslide in I lose about 4" of space (the bedslides height), so I feel like every inch is critical to not feeling utterly cramped in there when sleeping.

Potential solutions:
1.build pony walls on the sides of the bed, and span with pieces of plywood that are split across the width of the truck bed as opposed to along its length like in his picture. How thick of plywood do you think I need to not have any bend when we're sleeping on it?

2. build pony walls on the sides of the bed, and span 2x6 across and replicate the exact setup as in that link. Only thing is this way I lose an extra 1 1/2" below the platform for the bedslide, which either starts to become a really cramped sleeping space, or I have to find some really thin boxes to store under the bedslide.

How thick of plywood do you think I would need to not have any (or very little) give without any support underneath, or is this basically impossible and I need to run support? If I have a little pony wall on both sides, i'll be spanning a little under 4'.

Any help would really be appreciated, this road trip isn't going to be super long, so i'm really just going for an economical solution and easy access to our stuff, which I feel the bedslide provides without having to do a bunch of reworking and carpentry. Any better solutions i'm overlooking? Thanks!
Jacob

 

Anywhere in the area of 5/8-3/4" plywood should be sturdy. Especially if all the weight is distributed. (Ie, laying, not standing)