Thanks Chad - alas I don't have a spare Roden D.VII in the stash, and I stole a D.IIIa from one that I did have way back in the day, so I can't really go down this path either (unless I try and salvage an old junk one and perhaps cast some copies, as you suggest).
I also don't like how Roden (and Eduard) have moulded the ignition wire tubes down the sides of the cylinders as this looks blocky and unrealistic.
I see potential to take the Armour cylinders, perhaps graft them onto a modified eduard or Roden engine block (probably the Roden one, as the Eduard engine block is pretty rubbish), and do something there, but it certainly is a bit of a muck about.
There's so many aircraft that used the D.III and D.IIIa engines, I would have thought there would be quite a few on the market in 1/48, but alas there's nothing. The Vector D.IIIa appears to now be pretty much out of production. Even Karaya have stopped selling their D.III. We really do appear to have no option at the moment for a decent D.III or D.IIIa engine.
Looks like i'll have to see what I can do...
Cheers again!
BC