My own setup when diving sidemount with a pony is AL 80 left, AL 19 right. The right-side is redundant-only; and I don't breathe it except as practice or to verify it's working.
On my pony-side, my regulators have a 7ft hose, mostly tucked under bungies. Because the hose is tucked under bungies, there's almost no down-side to the long-hose. It's effectively a flexible hose-length, or about 32 inches when tucked., but pulling on the hose easily converts it from something like 40-inches to 7ft of usable length. The hose has never come unexpectedly untucked from bungies.
Do you need 7ft? No, not really. The original idea though was if I ever was in an air-share scenario (which I mostly dive solo), the standard "rule" is that they grab the reg on the brightly-colored hose, and that's theirs. If necessary, I can even remove the cylinder entirely and hand it off. My left-side would still be attached to my inflator-hose, and have my larger air-supply.
I use the same regulators when diving normal sidemount (2x AL80, or 2x HP 100s)
The reason I suggest you consider 7ft, is because it sounds like you want to play around with hose-routing. By doing this, you effectively have a flexible hose length, and can try everything from 5-inches to 7ft. The 70 or 90-degree adapter is irrelevant to hose-length, as it's basically adjustable. I have a 90-degree adapter on mine.