Usually with a sliding goose, the outhaul runs BACK to the outside of the boom. Somemtimes the outhaul has a 4:1 or 3:1 tackle inside the boom, before it exits... so that you tension the outhaul on the fly while sailing.
With the sliding goose, you can either use a standard cunningham (connected to a cringle above the tack), with the purchase of your choice (on a 24 footer, 3:1 or 4:1), or the cunningham can be connected to the bottom of the slider on the goose, and effectively do the same thing.
I don't think your rig for the outhaul should come out of the boom and go to the deck, it should connect back to the boom somewhere, the effective force should be to compress the boom into the mast (cause it's pulling the foot out away from the boom).
The outhaul rig will be similar to this (it's exposed to show how it works)...
My sliding goose (yes the boom is upside down, see the hole in the bottom of the slider, that's for pulling the goose down aka: cunningham, I use mine as a regular cunningham with a hook into a cringle in the sail):
Cleats on the boom for the outhaul (and flattening reef):