Selig Z Chair Cushion Dimensions?  

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You can see what's left of the webbing.

*spanky* & cdsilva gave aweso...
*spanky* & cdsilva gave awesome cushion advice. That helped me with the same cushion question. Thanks for saving me from the top heavy and clunky! I'm doing a Z sofa too. Would the same foam ratio apply to the sofa? Should it be one long cushion top and bottom, or three across?

My preference for the...
My preference for the three-seater sofa would be same foam thickness and firmness specs as the chair, with a single seat and back cushion; more comfy for me for lying down on. However, I also think dividing the cushions into threes works as well.
On a side note, I've seen and sat in slightly trapezoidal section backrests for both chair and sofa, and am not the biggest fan of that option. I prefer that design more when used for daybeds, where the trapezoidal section is emphasized and can be shifted and used as a headrest in bed mode.
I'm a big fan of the Z's, so would be interested in seeing pics of yours: walnut-stained beech, teak, or the ever-elusive solid walnut?

I would caution against
one long back cushion on a sofa of any sort, unless it was the original design. The reason is that on a loose back cushion, the cover tends to rotate downward around the insert with use. A lot of people start to slouch a little after they've sat awhile and this drags the fabric down. When you have single cushions along the back, this effect is less because the corners hold the fabric in place somewhat. On a long cushion there's less of that effect in the middle and you will end up with the top seams a couple of inches off line unless you want to tug them back into place every so often.
It can happen with the seat cushion too but not nearly as much as it happens with a back cushion.
One big seat cushion is ok but three look fine and then you have the added benefit of being able to clean or replace a smaller section if there are stains or damage. That goes for the foam too. And you can rotate them if you always sit at one end (like I do).

Wow! Thanks cdsilva & *spanky*
You are awesome! As for the wood, I have no idea. I'm still waiting for the seller to ship and it's been 2 weeks! Driving me crazy. They said it'll ship today, so... Also their pics were terrible. I'm including the two they posted in case you can determine wood, but the lighting is off. As for the material, I wanted to use faux leather due to pets and kids. Maybe orange? I like the look of buttons too. Please tell me if I'm making a mistake, as I have zero design skills. Be brutal, I can handle it. Thanks again to both of you!

Buttons will help a lot
to keep the fabric on the back cushion in place, but then you can't easily remove it if it ever needs dry-cleaning. You CAN do it, you'll just have to remove the buttons and retie them again. If you go with buttons, consider having them tied to buttons on the other side so you can flip the cushion and extend the wear.
A lot of fabrics these days are easy to spot clean so don't let that hold you back. And kids can actually be taught to keep feet and food off furniture! Dogs (probably not cats, though) can be taught to stay off, too. Not that you have to treat the furniture like museum objects, but there's a happy medium in there somewhere.
I would just stay away from synthetic suede. In my experience, it holds onto oily stains.

Wood is always difficult to...
Wood is always difficult to tell in photos, but it looks to have had some finish work done to it. My guess would be originally stained beech, but then re-stained with a darker walnut stain and then top-coated with a poly. Or the flash may be playing tricks on my eyes in terms of shininess of the finish.
Most of the Z examples shown above are stained beech, with the exception of spanky's Z ensemble photo which is teak with lighter wood backrest slats. I've read claims that this wood is maple, but that doesn't make much sense to me for a Danish-made piece.
Also, a quick way of telling whether a Selig or France and Son piece is stained beech or solid walnut if you are unsure is to look inside the keyhole joints. The stain usually never makes it back there, so you can see the true color of the wood itself.

an observation....
and it may be a wrong one but I've noticed that the z chairs with the fegas style straps tend to have the selig emblem embedded in the wood where as the ones with the dowel strapping seem to have the selig sticker or none at all. correct me if I'm wrong in this as i have never owned either of the type of chair but from all the photo references I've seen this seems to be the case. does this have something to do with the year the chair was produced?