It's not original development so it goes in general.
It's easy to make recoveries flashable if you have the recovery .img file. I use a modified kernel flashing zip file... johnnysit's newest recovery complains about the update-binary but is sophisticated enough to take care of using it anyway.
Drop the .img into the /kernel folder of the zip. Modify META-INF/com/google/android/updater-script by replacing generic_recovery.img with the filename of your recovery .img.
Rename the containing zip appropriately and sign or don't.
This template contains an empty .img and shouldn't flash. I wouldn't try it unmodified unless you're prepared to replace the recovery afterwards.
Hope this is useful.