Hello Steve;
Some time ago I purchased the "Compact" cutter made by Logan. It works quite well (at least for me) but with one serious drawback I didn't think of when purchasing it - you are unable to make a cut on a 32" wide piece of mat. This makes it difficult to make that first cut on a 32x40 mat. The solution led to a more versatile tool.
I purchased the Logan "Adapt-a-rule" which is a 44" long extrusion with the lip that the Logan cutters ride on. I found one of those old "laminated on each side" office dividers which I cut to about 36x44. To help understand the following, visualize this board laying flat on a table or other support with this Logan rule thingy laying across the middle of the board in the short direction (about 22" in from each side). I will be calling the "mat cutter" the thing used to slice mat material, not the bevel cutter. Make sure the rule is quite close to a right angle to one edge of the board (which will be the "front" of this thing) and route a 1/4" slot down the middle about 3/16" deep directly under where the mat cutter blade will protrude. On the front edge I attached a lip which sticks above the top surface about 3/4", with roughly a 6" gap in the middle, and put a short adjustable fence on the opposite side. These fences are positioned such that when the Logan rule is pushed against these fences, the cutter will slide directly above the slot in the board. The top fence is adjustable to allow me to precisely set the cut angle to 90 degrees.
Now I can lay a full sheet of mat material on this top, and with it against the "front" lip make a perfectly square cut across the width. Piece of cake. (I can give you instructions to easily square things up).
While this has been a dandy tool for making those initial cuts to a mat, I have also used it to cut more than one window in a mat, which would be a little more tricky on the Logan mat cutter I own. There have been a few large mats (24x36) for which using this table cutter was a breeze. The Logan rule is available in a longer version which if you adjusted some dimensions you could make a cut the "long" way on a full mat.
I suppose my description leaves a few questions, and if you want to see some photos just send me a note.
Last suggestion - make sure the router is pulling the tool TOWARDS the guide fence. I ended up with a little wandering groove on my top which doesn't affect anything, but doesn't look professional. I keep looking for another one of those nerdy office dividers...
good luck
rex