Parallel is not the problem
Retaining parallel is not the problem. End cuts as in cope and stick,lock miter, 45 degree bevels on a box corner. Retaining square and fit. To mention one of the problem areas. The top and fence I have right now is fine if I want to put an edge on a table, shape some crown molding, or build a nice baseboard. On and on. Edges are not the issue. Everything comes apart when I have to keep right angles and tight or square fits. Making a box joint, or half blind dovetail for a drawer corner, or ladies jewelry box.
I look at the nice work that guys are doing on their Incra LS systems, and I want to do the same. I built some wooden window sash for my home, and it worked nice but not easily repeatable, and there are a dozen more windows to go. These are the problems I am looking to solve.
Phil B.
Take a look at the Kreg fence...
If you do a lot of cope and stick doors you might want the fence paralell to the miter slot. The Kreg fence is paralell, and can be had with a micro adjuster.
If the paralell doesn't matter, there are others that are sturdy with t-tracks for flip-stops and feather-boards.