Thanks for bringing this back to life. I have been trying to record some tapes using manual recording schedules in Myth, but have had mixed results, probably due to user error. This will give me another option to try.

You're welcome. Since you expressed an interest, and probably others in the future will wanna do this, I wrote up the relevant parts into a new post here.

To do this on my system I added an input for my unused composite input
on my HD-5500 and I added a channel with a strange number for that
input. Whenever I need to record from composite now I set the A/V
inputs up and just select that channel in live tv.

If you only have one input, say composite that is already used for video
capture, you could just add a channel number that is unused and tune
to it after switching input leads to your other video source. The reason
you still need an unused channel even with this setup is that if you use a
used channel to record from and if that channel changes from one show
to the next, say at the top of the hour, you may have multiple recording
files that you will need to piece together.

If you don't like your live TV recording profile, you can set up a manual
recording (but I remember there was a bug with manual recording...)
a few minutes in advance and select a different recording profile.

Not exactly high tech, but it works.