Some limited forward progress to report.
I bought the A-Line frame when I was bitten by the "replaceable dropouts" craze that hit several ES members this past winter. But from the start it was always a stretch whether other efforts would suit my needs: Most people were creating dropout replacements for hub motors. From the start, my plan has been to build the bike with a left-side RC drive and NuVinci hub. So my notional dropout replacements would be something like the two pictures below. My thought being, I can simplify my dropout design by using off-the-shelf modular components that give me dropout, derailleur (== chain tensioner) hanger, and disc brake mounts. These are pics pulled off the web that I used as a design guide:
So drawing on inspiration/ideas from Oatnet, Magudaman, Andje, Sn0wychild, and help from Adam333 and especially Fractal, my path led to a custom design of my own and fabrication by emachineshop.com
(I plan to create a "review" thread of emachineshop.com in the near future - but the bottom line up front is it's a great service, thumb's up).
My custom dropouts give me about 3" more length and 1" more height than the originals. The right side replacements showed up Friday and the left sides should arrive early next week. Here's the thing mounted, with of course the original in the background:
Why the extra holes? Well they only added a couple of bucks to the order, so why not? The smaller holes on the upper edge (tapped for M5 bolts) are for possibly mounting a mudguard in the future. Anyone know a good 22" diameter, 3" wide mudguard? The larger hole is tapped for M8 and is there for whatever - I was thinking possibly a mount for a trailer hitch. I suppose if I was smarter I would have made the diameter and thread pitch the same as the original A-Line holes, making my A-Line dropouts literally able to accommodate a downhill hub as was original. Live and learn.
The mount holes on the new and old are vertically aligned. Big difference!
Comparing the insides: I had some material cut out but not nearly as deep as the original. Strength over lightness. When in doubt, over design. Note the custom parts, when mounted, are 150mm between the inside faces. The bolt-on modular parts by (from Paragon Machine Works) are 7mm thick, taking me close enough to the 135mm spacing the NuVinci needs.
Comparing the outside faces:
One more pic of the dropout, mounted. It's a really tight fit! I had to do a light sanding in a couple of places, no big deal. These will be a bugger to take off- but I won't ever need to take them off, so I don't mind.
So I'm waiting eagerly for the UPS man early next week. Once I get the left side dropout assembly installed, I'll be able to mount the rear wheel and at least have a bike I can ride rolling down hill (electric and human power propulsion still awaiting some parts...)