I looked at woodhaven and didn't really see any fences. I didn't spend a whole lot of time looking. The only thing I have of woodhaven's is their box joint jig which I bought at an auction. I use it for cutting through dovetails on the table saw. Here is a couple of pictures of it and I am wondering if yours looks anything like it.
If you have the metal fence then just saw the opening bigger on the table saw. I wouldn't use my best blade and just take your time and be sure to wear glasses.
The following is not a woodhaven piece. I bought 2 of them at another auction, but it is one of my router fences. I sawed the opening. The opening can be sawn at al angle to fit the raised panel cutter. It is the beauty of the following MDF panels
I like to use 1/2 thick MDF for the front of the fence It cut beautifully for zero clearance fences. If I change bits I jut cut off the used part and start over.
For others just looking here are some pictures of how it is fastened.
I do have to remove the dust collection to adjust the bit height, a flaw in my design.
Here is a picture of one of the feather boards I prefer to use on everything.
The table moved when being machined and was replaced. I got the old one but had to re-machine the slots so they are to wide I had new blocks to fit the slot and epoxied a nail into the screw slot so it can expand in the slot.
And just another look at the set up.
If I were to make another fence I would use a multi track from Rockler. With some of the others you have to buy special tee nuts after the fact as was I case with the one shown.
I have found that 18 inch fences do anything I have asked it to and so you can get two fences out of a 36inch piece.
Tom