I have the LMT DMR stock for both 556 and 308 versions. With the LMT MWS carbine tube on my LR308, if set it all the way forward/collapsed and locked the stock will sit flush to my GG&G MURP endplate. (There can be a slight gap due to fit of the buffer tube to receiver or thickness of the endplate but for the most part I consider it sitting flush). I do not have a KAC SR25 with the QD plate so I'm not sure if it will sit flush if you try to lock it all the way forward.
IMO it's a great stock. I always liked the angle of the cheek rest of the LMT SOPMOD and the LMT DMR has it. It's lighter than the Magpul PRS and you can drop it in to a carbine tube.
Hope this helps.
EDIT: The DMR stock is held into position by the lever (the oval shaped thing) that is forward of the cheek rest knob. It's under tension so you can place a tip of a round into it and push down to adjust the stock it in or out.