@Eric Sedletzky,
These things you describe, I have thought about, too. What I have concluded is that, when people were diving without a BC, they were finning continuously, angled slightly upward, so that the resulting vectors (from gravity and forward motion through water) had these divers traveling horizontally (more or less). Stop finning (with a full cylinder), and the diver would sink. As the cylinder empties, the angle would have to change, necessarily, I think. DH regs are located optimally per the illustration (and tuned) for this swimming position, I think.
I think that with the can located as per the illustration, a diver can angle a bit up and a bit down from that angled-slightly-up to angled-slightly-down swimming position, and still enjoy very good performance from his/her DH reg.
Since you and I both learned from "The New Science of Skin and Scuba Diving", we both know that when buddy breathing with a DH reg and traveling horizontally, the donor assumes a left-side down, right-side up position for best DH reg performance, as the buddy pair fins face-to-face.
I have no illusion that my 1st gen PRAM will ever breathe as nicely as my Scubapro Mk 10 Plus + Balanced Adjustable, or G250, or (especially) D400.
My interest in diving a DH reg really has to do with the how relatively quiet it is (bubbles routed behind my head rather than beside my ears), and by how fish, not frightened away by bubbles passing near my face, much more readily approach my faceplate. And I am hoping that my DH reg will be a better regulator for me to use when I am photographing U/W wildlife and structure with my new-to-me Nikonos III (a Christmas present to myself).
Being a solidly senior citizen now, I expect that I will
mostly use my DH with relatively lightweight, moderate-capacity cylinders (e.g., steel 72, Faber LP66, Luxfer Al 63, etc.) solo, at moderate depths, using a thin- to medium-thickness wetsuit. Consequently, I expect to use my BC sparingly--like I was originally taught (using a steel 72 and a 0.25" farmer John and long-sleeve shorty)--you know, using it for dives that might otherwise be done with
out a BC. My DH + relatively tiny Argonaut 23" wing worked perfectly (except for its too-short corrugated inflator hose) for me this past weekend during its inaugural open water dive, a very shallow dive.
I am looking forward to diving this rig a bit deeper, and eventually to moderate depths, soon, once I receive and install the longer corrugated hose I ordered.
And then using my double LP50's + solid-bar, single outlet, J-valve manifold.
And then adding, finally, my Nikonos III, for both the single-cylinder configuration and the manifolded doubles configuration.
rx7diver