Coop inside a run idea - suggestions welcome!

Hello All. I'm a newbie and am planning my coop/run. I'm in Florida so ventilation is important, I also want to keep budget as low as possible. Here is my brainstorm, should I rethink anything? I've been reading around the forum a lot and it has been so helpful!

Run: Somewhere in the neighborhood of a 6-7'x10' rectangle. Welded wire or hardware cloth. (If I do welded wire, should I line it with chicken wire on the bottom half?) Bury chicken wire 12 inches deep around perimeter and attach to run. 4x4s in the corner with support post in the middle. 1x3s along the bottom and top making a frame. Steel panel roof. Sand floor.

The question I have is really about the coop. If I have the coop completely inside the run, does it need to be off the ground? How tall do I need to make the coop? I understand the minimum space idea, but I didn't know if there is a preferred height for the chickens when they are shut up for the night?

I'm thinking from a clean up perspective scooping sand is the easiest for me personally. Could I build a low coop with a hinge top like this one http://artisandesignsdtb.blogspot.com/2009/06/new-urban-mobile-backyard-chicken-coop.html but not have a bottom on it? The hinge top would let me scoop inside the coop. If I did that, would the nest boxes need a bottom? Is the floor mainly for predator protection or does it serve a different purpose? If I make the run secure enough, I'm not worried about digging predators in the coop itself. After thinking about it, I will probably attach wire as a flat "floor" to the coop and just cover it with sand. Will that keep out any digging predators that could theoretically make it past the run?

I'm only getting 4 hens (the chicks ship today, huzzah!!) but am building for more as has been the #1 piece of advice

Thanks for your input!

 

My back and forth about the raised or not is this:

On the floor is easier to build with what I have in mind.

Off the floor I don't have to worry about flooding, but is that an issue? It will be on sand and we are not in a flood zone.