Yup, I am the one and only. Apparently "Captain_Throwback" is too long a username for this forum.
So, how to do it - it's actually not that complicated. The key is the android_info.txt file in the PC36IMG.zip file. That determines the "Main Version" number, which, when you're S-ON, is the lowest ROM version that it'll let you install (either via RUU or through HBOOT). The key is to choose a low number. In the attached zip, I've used 1.00.000.0. There aren't any ROM version numbers that low, so you should be able to use any RUU or PC36IMG with a valid HTC signature to update the device once the NAND is re-locked (even Eclair, I believe).
I hex-edited a downgradable HBOOT version (0.97) to be 6.97, so it'll install & overwrite Revolutionary. It *may* lock your NAND (i.e. S-ON), and if it does, then you can just go ahead and run the latest Froyo RUU (3.70) and you'll be all set. If not, you'll need to run the unrevoked S-ON zip, which should re-lock the NAND. The catch is that your radio needs to be 2.15.00.11.19 or older. If you're running Froyo, that's no problem. If you happen to still be running Gingerbread, you're stuck running a Froyo RUU to downgrade it, and then you have to re-lock the NAND, and then re-run the RUU.
That's all!