I had to lower the pre-buffering to 2 seconds otherwise JRMC15 would not work with M2Tech Hiface.
I can't think of a technical reason for the amount of prebuffering to alter the behavior of the output plugin. I suppose it changes the time between open and buffer fill slightly, but this should not matter.
But if you use small prebuffering values, you may get data shortfalls (which can sound like stutters) when switching tracks.
Maybe you could test a little more with 6 seconds (or more) of prebuffering? I think that would fix the stutter between tracks.
We'll also test our Hiface and see if we can reproduce the problem. In general, we've had good luck with it since getting the latest driver.