It'd probably help for me to post up my numbers. (It's rather sloppy that I didn't, and I apologize)
My notes say that my assumed mass figure for ²H was 196.7 kg/m³. I can't for the life of me remember where that figure came from. I'll recalculate with standard deuterium densities, I think.
I'm actually still debating on whether or not the effects of mass, volume and field geometery on warp propulsion.
The thing that kind of troubles me about the power consumption figures in the TNGTM is that the implication throughout on warp drive is that fuel isn't the limiting factor for higher warp factors. This implies that it's coil components or hull stress that starts causing problems at super high warp factors.
However, a comparison of the energy requirement chart vs. fuel capacity (even assuming high density slush deuterium at the nearly 200kg/m³ I erroneously had above) suggests that fuel capacity would become an issue significantly faster than supposed other factors would be. Warp 9.6 for can't be sustained for the 12 hour limit because fuel exhaustion would kick in at the 4 hour mark.
Also the other problem is that the physical size of the warp core seems extraneous with the fuel figures we have. Even a reaction chamber of only 1 cubic meter would expend all 6,000 m³ of deuterium in an hour and a half at maximum throughput. (Noting that the reaction chamber is supposed at least 2.3 x 2.3 x 2.5m in dimensions, it's probably substantially larger than 1m³ in reaction volume).
We also know that the Galaxy
-class puts warp reactor output to 75% when they go into Red Alert. And that this readiness state protocols require procedures in case of duty shift changes. In which case we should probably assume the ship can sustain that level of output for multiple duty shifts (4 hr intervals, presumably). But again, even a minimally sized reactor would eat through its entire anti-deuterium supply in a bit over 2 hours at 75% output.
Something's not right here.
Need to figure out what it is.
I'm going to be posting more of an in universe examination, that kind of glosses over the whole tonnage issue soon as a side bar in the procurement thread (I do think size and mass should have some impact on warp propulsion, but that there's probably something in the order of subspace field stress that can shake a ship apart (see: Defiant).