I just played the Gatling Gun scene again in Book of Eli with the DTS core. It triggered clip protection and an adjustment of -0.1 dB. SPAN showed the clip to actually be 1.9 over 0 dBFS.
I would recommend you setup your system to decode DTS-HD. That should eliminate the problem. However, an adjustment of even a few dB isn't going to hurt anything unless you listen with the volume all the way up on your McIntosh and feel like you need 2 dB more.
If staying with DTS, I would add a Parametric Equalizer "Adjust the volume" entry at -2 dB for all channels. That should take care of the problem. Then disable internal volume. This ensures that the volume is always at max and you don't inadvertently lower internal volume.
I just tried the same clip with -.5 dB in the PEQ. Now JRiver does an "adjust volume by -0.0 dB for clip protection."
I think there is still some clipping going on as shown in SPAN. If I lower the adjustment to -2.0 dB, then JRiver no longer does any adjustment for clip protection.