said by EG:
There isn't very much wiggle room left for the upstream power..
Agreed, and a -3.5dB leg of a splitter would bump the downstream right down to a nominal 0.0 or so, while giving more room for the upstream. May even pick up that 3rd US channel in doing so...
*edit* Assuming of course the OP's CMTS supports 3 bonded US channels