LOL Jekyll.
Artoo,
Pulling up before guns range is very dangerous IMHO. If you mis-judge his E state he can just zoom up under you and gun your bellybutton down. I avoid the HO as well, but normally I do it a bit different. I make sure I get my speed up and I'll dive a bit to come in beneath his nose slightly. I'll do some evasive starting about D 1.3 and transition that into a vertical lead turn, a slightly oblique immelman, as he hits D500-300. I'll then come over the top as gently as I need to depending on my plane and E and how hard the other guy reverses.
Now comes the hard part. If the other fellow is close in E and is a good pilot, he will likely have done the same thing, so we'll tend to be looking at what could be another HO situation. What you do here is critical. If you do not have enough speed to go vertical again, you must press for the shot if he has made it to your altitude. Preferably you want to hit him before he gets all the way around and can shoot you. Alternately, you will have turned a bit slower but conserved more E, so you can manage another vertical move. The trick now is to avoid this second front quarter engagement and go vertical again. If you avoid his shot he will have dropped his nose too much to shoot you, and you own him. I normally try to get slightly out of plane with the bogey at this point, to one side and banked slightly to keep him from lining up too easily. Ideally you have more E at this point and he'll wallow below you for an easy kill. DO NOT take the HO shot at the second merge if you have the E to go up, unless you beat him by a lot and he can't shoot back yet. If you try for the front shot and miss, you will have given up enough of your E and angle advantage that you will be in serious trouble. Remember, whenever you take a HO shot, you give up position and E to the guy that does not take it. If you are going to take the HO it should be your last option and you'd better not miss.
I know it's tough to avoid the HO at the top of that oblique immelman fight, but you've got to resist shooting back and avoid if you have more E. Instead of firing at him or lining up your pass, you should be building a bit of speed and getting out of plane a bit, making read for that next vertical move that he can't follow.
SKurj's advice is also good. In the P-47 that I fly, I use the low-G pull-up into a zoom depending on the situation. If I have enough of an E advantage that I can burn some and still be ok, I'll do as I explained above. If not, I'll do what Skurj describes.
BTW, the initial merge is a very good indicator of the caliber of the pilot you are facing. If the guy you merge with tries the below-the nose evasive and vertical lead turn just as you do, it's time to start worrying. <G> Better yet, you had better be thinking 3 moves ahead, because the other guy might be. If the enemy dives at you and goes for the HO and then overshoots below you before reversing, it screams newbie. Proceed as normal and he should be an easy kill.
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Lephturn - Chief Trainer
A member of The Flying Pigs
http://www.flyingpigs.com 
"A pig is a jolly companion,
Boar, sow, barrow, or gilt --
A pig is a pal, who'll boost your morale,
Though mountains may topple and tilt.
When they've blackballed, bamboozled, and burned you,
When they've turned on you, Tory and Whig,
Though you may be thrown over by Tabby and Rover,
You'll never go wrong with a pig, a pig,
You'll never go wrong with a pig!"
-- Thomas Pynchon, "Gravity's Rainbow"
