Ok, I tried it out this morning. It worked like a champ! I was having trouble scanning the Kodachrome with my Epson V750, getting the colors anywhere near correct was next to impossible, and I tried the Epson software, Silverfast and Vuescan.
I used a Canon 5DMkII with a 100mm macro lens at f8 set on a tripod, with the slide in an old negative carrier placed directly on top of a cheapo Hakuba 5X7 lightbox. I focused manually using 10X Liveview.
I am happy to say that with only very minor adjustments in Lightroom, I now have a "scan" that looks pretty much exactly like the actual slide.
And here are a couple of crops so you can see the detail:
The slide was originally shot with a Fuji Klasse W point & shoot camera.