On modifying internal mics..
I was never a much of a fan of the R-09's internal omnis, but placing a simple wedge-shaped cardboard baffle on the recorder effectively turned it into a miniature J-disk setup and greatly improved the resulting stereo imaging. I never actually recorded any music with it that way, but I kept the folding cardboard baffle with an R-09 shaped cutout in my recording bag for as long as I was using the R-09, just in case I ever needed to use it along on a table in a pinch. Didn't improve the quality of the not so great capsules, but provided vastly improved imaging.
Same should work for the internal omnis (or upgraded internal omnis) on the M10 or any pocket recorder using omni caps. Just arrange the baffle so that the openings to the omni capsules are as close as possible to the surface of the cardboard on each side. The folding wedge format helps to get the caps as close as possible to the corner intersection of the baffle and recorder housing as you can adjust the wedge angle to suit. As I recall the M10 has one small hole for each mic, so arrange the baffle so that the hole is right in the corner created by of the cardboard against the recorder housing, without obscuring the hole. That way you'll eliminate reflections off the hard-surfaced baffle, while harnessing some boundary effect providing increased clarity in the upper frequency range (down to a frequency corresponding to the size of the baffle), which should help counter "internal omni muddiness" somewhat. I suppose it's really more of a miniature
PZM Wedge setup than a J-disk.
Here's my old thread on baffles for R-09 built-in mics from 2006-
http://taperssection.com/index.php?topic=70134.msg939775#msg939775A few photos from that thread-
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You may recall Chris Church's "Micsketeers"mod for the original Edirol R-09 offered a few years later in '08, in which he removed the internal omnis and replaced them with a pair of his cardioids. Here's the original thread-
http://taperssection.com/index.php?topic=98290.msg1309708#msg1309708And a few photos from it-
The recorder housing needed to be modified to provide the appropriate angle for the attached cardioid capsules, and the rear vents need to be keep unobscured.