I'd also like to see pix and a part #, I did something similar without the caddy but might find your soultion a little more 'elegant'. I nipped away part of the stand bracket above the standalone modem area, and also in the door area, and have been able to get a 12.5mm drive mounted under the shield and can access the drive connection through the door.
I'll try to get some pix of my mods up on Yahoo today/tonight, the Kodak camera I borrowed is both crappy (493x373 in 'high' mode!) & cranky to d/l. Got a pretty nice Agfa cl20 on the way for a sweet price, 1.3megapix and USB will be a huge improvement....
"Holiday pictures, eh? Nudge, nudge, wink, wink" - Monty Python