I actually intended to use that DBM on my 6.5wsm & was talked out of it. I've been told they had some issues with the mags (LA IIRC) a while back, I don't know whether they were fixed or not. Seekins products are usually of good quality so I would have a hard time believing they haven't at least looked into it.
For the OAL needed they're about the only DBM in town, the APA (while having a substantially better mag release) is still built on the Badger M5 footprint running the AI mags. While of substantial quality, the ~2.8 OAL is WAY too small to house th 3.100 rounds out of my 6.5WSM.
Back to the drawing boards... stay tuned, fun (read expensive) idea in the works.