Well, I finally gave my circular cutter (Logan 201) a try, and of course I dove right in the deep end, with a double mat. The top mat is Romanesque Grape (seems like a deep blue, until you put it next to another blue, then its purple tint is revealed) and the inner mat is porcelein. The mats were from my stash.
The narrow wood frame has a light mahagony finish with beaded gold trim on the outside and a inner gold line. I wanted something warm to highlight the rocky promontory. This frame was an absolute steal from the pictureframes.com outlet shop: ~$11 for a 14.5" square frame. The plexiglass (not yet inserted in these pics), from americanframe.com, was ~$8.
The Logan 201 circular/oval cutter took a little practice. It's a four step process- you make 4 cuts, each progressively deeper. The blade depth is set by flicking a little lever on the side of the cutting head- it has different stops. The first time, following the directions, I simply lifted the lever with my index finger and it went straight through all the stops- which ends up with an rough cut. I learned to move lever more carefully using my index finger plus thumb for counterpresssure. As for the double mat, I tried to do it like I would on my regular cutter- cut the larger mat, affix the smaller (inner mat) with 2 sided tape, and then cut the smaller mat with a slightly smaller dimension for the opening. With that method, the mats should be perfectly aligned - at least on the straight cutter. On the circular, you draw horizontal and vertical cross hairs from the center of your mat and align the cutter that way. The way I did it, was to draw diagonals from each corner to find the center point, and then drew cross hairs with a quilting grid ruler. For each cut, I started from the corners of the larger (blue) mat, so in theory, the centers should have been the same and the cuts should have been perfectly aligned. But they came out a bit crooked (more of inner mat exposed on one side). What finally created the best outcome was to cut the mats separately then press together with 2 sided tape after visual alignment.
I'm glad I invested in the circular/oval mat cutter, though it seems precision is more of a challenge compared to the straight cutter.