Its all about position, position, position. I'd concentrate less on range and more on the position and attitude of the opposing plane.
For instance, if I were merging with you, and managed to get about 200 ft under you going into the merge, our circumstances would be different. You will need to pass through the merge point to keep from pulling up in front of me. On the other hand, from the lower position I can start my turn before the merge point, as soon as I see you about to cross into my projected turn arc.
If we were both skimming the deck, we would both be in a situation where we need to be wary of pulling too early, or too late. What range is that? Depends, do we have a combined closing speed of 250 mph, or 800 mph? Adding to the mix is the head on shot. In AW, 97% of head on hits were disallowed by the game. There is no such feature in AH.
So, going in, you want to consider avoiding the HO, approaching the merge point to allow you to pre-turn if possible, and a mental picture of where each of your turn arcs will look like to give you an idea of where you do and don't want to end up 1 second after the merge.