For Fred and anyone wanting to do a Single Sheathed car, here is what I have done or suggest.
—Use .015 x .060 strip styrene to build up the side Board x Board on a base of at least .030 styrene sheeting. At 1/87 scale wood grain would be barely discernable so I drag the strip styrene over some 320 (or 220) grit sandpaper two or three times wiggling it as you drag it for variation. This is just enough texture and avoids being a caricature. Then mark one edge of the backside w/a Sharpie to make it easy to know which side has been textured. Next chamfer one edge of the sanded side by running a sharp blade along it a couple of times. This can be the edge you marked or the other edge but it needs to be consistent because the chamfered edge can be hard to see. By having one square edge butt against one chamfered edge a slight gap will be visible between each strip or board that I think replicates the subtle joint between the boards on the real thing.
—For the braces I would use three different sizes of styrene. For the pieces that are attached to the side, I would cut strips of 0.005-sheet styrene to the appropriate width. These strips once cut to length and appropriate angles should be glued down directly to the side using sparing amounts of Testors to avoid distorting the very thin 0.005 styrene. Next tack down .020 x .020 strip styrene onto either glass or a smooth piece of steel w/Testors. This will hold the .020 x .020 in place while .010 x .030 strip is glued against the .020 x .020. Allow this to cure overnight and peel it up with a singe edge razor blade. This assembly is then cut to the correct lengths and angles and is then glued down to the .005 pieces already on the car side to complete the Z-Bar.
—The small square fasteners are difficult and fiddly. Three suggestions:
1.) Have them photo-etched—consult w/others about this method
2.) Make them with .005 styrene
3.) Ignore the fact that they are square and use round rivet shapes either from decals or harvested from styrene
DO NOT wait to solve the fasteners issue to begin the side pattern.
Back to the side: Using the .060 wide styrene may result in the portion on the side being slightly too tall: To compensate either the top plate or bottom plate can be slightly undersized.
On the attached photo note the fourth board from the top is slightly inset. It is .010 x .060. I did this to provide texture and I think it works. Next time I might have two boards like this spaced out. In order not to have the .005-styrene pieces that span this board distort there is .005-shim.