The HH is a perfectly valid tactic..and it was used in WW2.
It is harder to pull in AH because there is no sun... the hammerhead is a dangerous manouver to pull...for if you think about it, you are placing your own airplane in an extremely predictable flight path (UP!) but you also cannot manouver to evade incoming fire because if you do, you will slow down TOO fast and literally serve yourself as an easy kill.
In real life, the sun will make the opposing pilot have a real hard time bearing his guns on you..because of the sun glare. In AH, no sun glare means the virtual pilot has to rely exclusively on his SA (situational awareness..aka knowing opponent's E, alt, plane and sometimes even skill level) and timing..and luck (*cough* helon1k spraying cannon d1.1).
SOB: "Anyone have some pointers on setting up this manuever? "
I use this manouver a LOT in my P-38, I dont know if this will help you but this is what I do:
Firstoff the HH is not a manouver I 'set up'. If you plan to HH someone to death before the 1st merge, there's something really wrong with you (or you got Citardria's ego

). The HH is something I consider an emergency manouver.
Since the con is on your 6 already, the most important thing to make *absolutely* sure is that YOU have more E before attempting the HH. Best way ive found to do this is to do a sharp turn (preferably to the side the opposing plane is worse at turning due to torque) taking advantage of the 38's snap-turn ability and split-S followed by an immelman. The con in your 6 will very predictably go into lead persuit (aka point nose in front of your plane, pulling more g's, bleeding more E to get a shot at you).. This is to make him burn his energy and give you more advantage due to the 38's better acceleration (again, depends on enemy plane.. i will never HH a spit, 109g10, n1k or 190d9 unless im absolutely desperate).
On the top of the immelman I level and wep accel.. when the con in my 6 finishes his own immelman i wait for him to level and I go split-S again and repeat the immelman.
By the 2nd split-s & immel you will have made the con lose his E advantage and to boot he will likely think that when you split-s for a THIRD time that you are going to immelman again.
So, split-s for a third time, only dont wait for the con to follow you in the dive, get your speed to about 350mph and pull hard up into a zoom climb and bank the plane on its axis so you only show your side profile to the con as you zoom up. The con will at this point be either just starting his own split-s or be just entering his dive.. in short, has had no chance to gain speed. When the con sees you pulling up he will pull hard up on his stick to try a shot on you.
You will either get hit or zoom up past him.. cons very, very usually follow you up in the zoom firing... i almost always do lazy vertical sciscors to avoid being hit... and I watch my 6..when the con starts to LOSE distance i ready myself to flip over.. watch con..his nose starts to wobble or any other indication that he's starting to have control problems, I lower my throttle to 0. This makes the con suddenly GAIN on me, but its too late for him to get a shot, as usually the pilot on the other end either tries to spray and pray for a hit as he stalls or is too busy controlling his plane to notice he suddenly is gaining on me even though hes about to stall.
And the whole timing issue is right there. If you HH with your opponent being d800 behind you, chances are that by the time you flip over, he will already have nosed down and gained speed... effectively reversing the attacker/victim (which is good for you) but you wont get a shot at him. By timing it so your own plane stalls almost at the same time as his you will give yourself a perfect chance at shooting the con down as he tries to regain control after the stall (and the 38's superior low speed handling, no torque and superior initial acceleration will let you flip over fast, be in control and close in on the con before he starts to gain speed). Ideally I try to cut my engines when con has not been gaining on me in the zoom climb for little while or the instant I see him losing control... the 38's brick-like drag will slow you in an instant to stall speed.