I can report success. I created the header in a hex editor ( I had to write a little C program to do the checksum), concatenated it with my raw image, transfered it to the mac, and created the resource fork as per the wiki. It loaded right up in Disc Copy and reported the correct checksum. I had some problems booting the disc, but I tracked that down to a loose cable. After I fixed that it booted right up.

This is going to be a convenient way to make disks for my Tandy until I get serial set up on it. So I'll probably be expanding the program I wrote to do the whole conversion automatically. When I do, I'll post the code here in case anyone else finds it useful.