[Frizza]

Just thought I'd point out a few things worth considering.
The first has to be your filtration platforms, in all honesty I dont really see the point in using it. If you want to run some media (like carbon or a phosphate remover) then I would recommend you getting a reactor, these are very cheap and will be far more effective. It may also help with your maintenance schedule as well.

The second point is your return chamber, personally I would make this as big as possible otherwise you will find that you will be constantly filling it up due to evaporation.

The chamber for your skimmer really only needs to be wide enough for a pump or two. You could even use a single pump that is T'd off with some valves incase you decide on a reactor.

A note on what Froc3 said is also important, what you could do is move your chambers in a different order. What this means is that your return pump can be T'd off to your refugium chamber, install a valve so you can regulate the flow, and the refugium will overflow back into the return chamber. The only thing with this is you will probably need a more powerful pump so you get enough turnover, or go for a smaller pump just for your refugium.

Keep us posted with your plans, it is a great project, I thoroughly enjoyed making mine and I went through many revisions before deciding on my final plan.