Time for an update.
More fun with vector art:

One of my goals for this build has been to see what uses I can find for the Silhouette cutter in this hobby, and the CDL lower surfaces seemed like an opportunity to put some more complicated masks to use. I have spent nearly as much time working at the computer as I have at my modeling table, but enjoy this type of work, so it suits me. The intersection between computer design and the physical world has always been appealing to me (Bo, your 3D printing is completely fascinating to me...), so the cutter is right in the sweet spot for me.
I started by scanning the various kit parts to get a template from which to work, then used various internal photographs and design plans to work out the internal bits. Once I was satisfied with the artwork, I printed... er.... cut out the design on Tamiya sheet tape:

I used clear frisket film to transfer the weeded masks to the model:

From here, it is straightforward airbrush work. Thin, loose layer of Tamiya Deck Tan (XF-55) for the areas between the spars where the darker upper wing shows through; remove mask and follow with a thin coat (3:1 thinner/paint) of XF-2 flat white to tie everything together.

As you can see in the vector art image above, I also cut a mask for a oil seepage stain on the lower wing. This took a bit more planning: Deck Tan and thin Flat White coats first without any masks. Mask the outline of the stain, and spray Desert Yellow (XF-59). Remove the stain mask, and put down the mask for the spaces between the spars and framing (this stays in place until painting is done). With this in place, cover the still exposed "stained" parts and spray a coat of XF-2. Uncover the stained spar areas, and cover the dry spar areas, spray Dark Yellow (XF-60) to represent the wood framing beneath the transparent wet linen:

All of this will eventually be covered by Aviattic transparent CDL decals, so I sincerely hope I have struck the right contrast/color etc. The additional pre-decal staining seen above was done with oil washes and colored pencils. I will cover the stained section first as I think that has the most potential to miss the mark for the look I am hoping for, and I want to make sure I have extra decal material if needed.
Overall, the masking went fairly smoothly, and without too much trouble. In the first image, you can see where I modeled the internal spar in a number of pieces (between each rib) with the thought that I'd spray the first coat of Deck Tan, then remove them and "bury" it a bit with a second coat. These proved too thin and fussy to be effective: either the cutter had trouble generating cleanly separating the .75 mm wide pieces, or I couldn't keep them in place while transferring them to the model. I wound up just using .5 mm tape which was far simpler. (One could argue that the same could be said of the tried and true strips of tape method of making the rib tapes; like I said before, I wouldn't have done it this way if I didn't enjoy it.) I also took 2 attempts to get the stain masking procedure figured out: my first attempt involving removing and replacing the frame mask left visible lines where I did not get it perfectly lined up the second time.
That's it for now. The artwork for cutting the Aviattic sheet is already done, but I have decided to paint the upper surfaces first as I want to minimize the handling once the decals are on. Hopefully the next update won't be as delayed as this one was (I was away for 8 days on a family vacation after my last post.) Thanks for looking in, and as always, questions, comments or suggestions are always welcome.
Chris
p.s. Does anyone have any suggested (Tamiya) color mixes for the red and blue of the roundels and rudder? Thanks in advance.