I found an easy no-mods source for ~5", already crossed-over IDE cables, for those of us who have access to junk bins of really old laptops:
The cable that connects the hard drive in an old Ultra 486sx laptop (made/sold by Midwest Micro, IIRC, but I don't know the model number), and also the identical model rebranded by Tandy (or maybe it's the reverse, Ultras are rebranded Tandys. Anyway...) have a ~1" long, flat cable with one male and one female mini-IDE headers, and it's wired with the pins switched as the IOpener requires. Also in the same laptop happens to be a ~4" mini-IDE cable, wired normally and female to female, which is perfect because it happens to have individual wires instead of ribbon cable, so it's very flexible so you can get creative with HDD placement. Just plug the 4" cable into the male header on the 1" cable, and viola, a 5" long, flexible, crossover-wired cable! Or connect your normal 2.5" to 3.5" adapter to it and (with an external power supply) use a standard IDE drive. And, on that note...
From the same pile of junk laptops, I found some Dauphin 386sx laptops that each have a 2.5" to 3.5" F-F 44-pin IDE cable. Snip 4 wires, hook up 5V from a power connector, and crimp on a 40-pin IDE connector for the 3.5" drive in place of the 44 (or just cut off ~1/8" of the 44-pin connector), and you have a cheap and easy way to hook up your 2.5" drive in your real computer.
So, everyone run and check your scrap heap and local obsolete-used-PC superstore! ;) And anyone else who frequently scraps laptops and happens to know of models with useful parts for an IOpener project can feel free to post to this thread as well.
PS-Roastbeef, please email me, if you would be so kind, I have a couple of off-topic questions I'd like to ask you rather than post 'em here and get flamed. ;) Thanks!