Larry's thread prompted this - i've not used an outboard shaper fence. As in a outboard second fence mounted in the miter slot. This isn't in the context of a specific job, it's more an 'I wonder what uses the method has' and 'how it's done' sort of question. (didn't want to hijack Larry's)
One very nice example seems to be cope and stick cutting - in that case it seems the work is kept pushed out against the outboard fence using a power feeder. (tracking out a little rather than the ususal in) One advantage in that case seems to be that the stock can be a little irregular in width since the cutter places the profile a set distance from it - and so guarantees a consistent finished stock width. The main infeed fence in that situation may be set back a shade to let the stock through (?), while the outfeed is presumably stepped in enough to support the work coming off the cutter. (?) Looks like it's a technique that needs a power feeder.
It seems a very elegant method, this guy demos it very nicely on cope and stick: https://www.youtube.com/watch?v=28uLpNzHXnY He's also using a nifty set up where both the coping and the sticking cutters stay mounted on the spindle. His coping sled sets the work at the right height for the top coping cutter to work, he then in a minute or two switches to using an outboard fence at table level to use the lower cutter to handle the sticking. He suggests using shims to fine tune the relative height of the two cutters.
Another neat looking solution. He uses a T track screwed to the bottom of the outboard fence as the key to engage in the mitre slot, and then a couple of simple work clamps to lock it down at the ends under the shaper table....
Does the method open up any other nifty options?