Most BD rips of lossless tracks favor very high bitrate conversions to DD. Usually the max of 640kbps, but it's really probably overkill. 640kbps DD is considered comparable sonically to 768kbps DTS.
IIRC, you don't need any plugins or anything special to extract a DTS core. Just the main eac3to program and:
[code]eac3to input.dtshd output.dts -core[/code]
See if this makes sense: DTS HD MA is really just the old DTS audio with some extra stuff tacked on that makes it lossless instead of lossy.
But, the thing is, within all DTS HD MA tracks there is a plain old DTS track embedded.
You can toss out the lossless component and be left with the DTS track. It's not re-encoding to get to standard DTS, it's untouched.
Um, to put it another way, it's the old Voyager 6 sitting inside the massive AI ship that is V'ger. You can pull out the old Voyager probe and use it, but of course it's not nearly as impressive... and doesn't kidnap bald women.