What's really ludicrous is saying that a mechanical fan sucks up 15 or more hp ;
1) that would have to be a max-effort direct drive fan,
2) spinning on a stationary engine., like on a dyno, so you can measure it.
3) at peak horsepower say 5000plus rpm.
That will never happen in real life, because;
1) your engine will never ever be at 5000 rpm, in still air, and working. It ain't a generator.
2) I can't see any HotRodder ever putting a 7-blade, hi-attack, all-steel, direct drive fan on his engine, without a clutch, cuz nobody wants to see a 7-blader blow up, at 5000/6000/7000rpm .. and the smart money is on a thermostatically controlled clutch.
3) your V8-street car by 5000 rpm in first gear, has more power than the chassis can handle, so right off the bat even a direct-drive fan is not costing you any ET. It's all going up in smoke at the rear tires.
By 5000 in second-gear with say 3.55s and a TF-auto, your street car is doing about, lets see now ,oh I know; waaaaay past the speed limit, so again even the direct-drive 7-blader is costing you nothing. But Ok , I get that not everybody lifts at 65mph, so 5000 in second comes to about 78 mph. So the airspeed hitting the rad is 78mph. I got no idea what the airspeed is on the engine side , and I don't care; that clutched 7-blader is simply going along for a free ride, costing you nothing, because it has long-ago de-coupled. Yes it's windmilling so what! there's a 78 mph wind ramming thru the rad doing a fine fine job of cooling it.
4) My clutched 7-blade,hi-attack,all-steel fan, has been 100% reliable since the day I installed it, keeping my engine at exactly the temp I adjusted it to; I mean exactly. And I never even look at the temperature gauge, anymore.
But back to OPs question;
As you have detailed in post #1, and with supporting statements following;
if I was in your quandry,
I would try it
