Ok, for all who asked...
First, I'm modelling in HO scale. I found for logging modelling, that this offers some of the best choices, in a budget that I can afford (not to mention space requirements).
the enginehouse, so far, has been a 1.5 year project. I got inspiration from the McCabe engine house kit (from pictures of it at least), from John Allen's own scratchbuild project, and from (I believe) an RMC article (the exact one I will find and post later).
It is all built out of scale lumber, and each board is individually stained with a minwax stain stick, and the whole thing is yellow wood-glued together.
The foundation is styrene, with a "natural stone" styrene sheet overlayment. I discovered if you run the dark walnut stain stick over this, then wipe it quickly with a paper-towel, it has a nice weathering effect. ( as seen here
http://www.dragonmnt.com/Pictures/Models/Foundation-1.jpg )
the triplex came from my desire for the rare and unusual locos. I loved watching the mallets and Big Boy crawl around an oval of track. All those rods moving in different directions is almost mezmerizing.
Well, my father-in-law happens to model Erie-Lackawana, and when I saw a pic of the Triplex, I fell in love. Being poor, I couldn't afford a $1000+ brass model of one, and I happened to find this Riv. Mallet for only $60 (which is why I was able to take a razor saw to it!). Another old shop had pieces of a mallet, which is where I got the second rear driver set for under the tender.
Other than cutting away the piping under the cab, the loco itself is fairly un-modified. I could put the trailing truck back on, and put a normal tender behind it, and most wouldn't even know it was changed.
My plan is to rebuild the frame I made for the tender. I was experimenting with brass construction, but I'm not happy with how it turned out.
What I'd like to get are either drawings, or high detail pictures of the undercarriage of a triplex model to work from, and I plan on scratch building a new frame from styrene.
I decided that, since this tender has a significantly higher water capacity, I needed more than a two wheel trailing truck. Again, by leaving the trailing truck on the driver set, I could easily put that set on the mallet to return it to stock. Plus, the two-wheel trailing truck and the 6 wheel tender truck just makethe back end of the model look kewl.
One other mod I plan is to grind down the pizza cutters. This thing will barely fit on code 83 track (which is going to be the mainline for my layout), and might have problems on any code 83 turnouts. Plus, it looks too toy-ish.
For your amusement, enjoyment, or inspiration, I've taken a few more pics of the triplex, plus some of the old Mantua 2-6-6-2 I've rebuilt, and posted them here:
http://www.dragonmnt.com/steam.html
once the enginehouse is completed, I plan on displaying it at a local railroad museum while I construct my layout. He's had numerous model displays (and in fact has a HUGE HO scale layout) and has already expressed interest in displaying this once it is ready.