More info would be handy @RickB ..........
For an external Anderson to run say a compressor I would use some 8 B&S cable, stick it in some corrugated conduit and run it thru the floor to where you want it, zip tie the cable to underneath the rig with an appropriate fuse inline, direct to battery is usually the best way to go then you can draw as much as you want.
Sorry Drifter. With the outback I think there is the gap between the internal floor and the underneath ply, ie. the front storage space gap to get the cable through.
Okay, on my rig the front boot is metal lined and the floor ply is about 19mm, thicker than what Jayco usually uses, all I did was drill thru the lot and used a wall grommet like the ones in the pic but with a longer shank. If there is a gap between panels I would just pump some silastic into the gap before inserting the tube.....I seem to recall my old 14.44 had a double skin also as the boot was lined but with a plastic liner..............someone here has surely run some cables thru on theirs .