the key is on the first merge do a low-slice back into where the other guy will be. This will sling shot you into the vert, where you can then roll so that your lift vector is 2 plane lengths behind the other guy, then don't pull back to go down until the other guy starts to pull up at the bottom, this will allow you to conserve e.
The other thing is that you burn less energy over all if you can turn by having your nose vertical and rolling into the direction you want to go, instead of flat turning to that direction. Also, opponents that choose to drag you into a flat turn you should avoid by executing displacement rolls and keeping your e. If you can roll faster than they can turn, you can get your nose in position for a shot. The most important thing I can say is that visualize 2 eggs, one around your plane, one around the enemies, now try and roll your nose into where the eggs intersect.
here is a dumb example...
plane A = spit 9
plane B = 190 A5
190 is coming in hot on a spit 9, so the spit 9 turns to the right as hard as he can. the 190 seeing this, pulls up and rolls so that his lift vector is pointed away from the spit9. Once the 190 is nose high, the 190, continues to roll and pull back on the stick to place his lift vector 2 plane lengths ahead of the spit. The the 190 pulls back forming a awkward barrel roll and is in now in a mild climb (slinging out of the bottom of the barrel), with his nose pointed to where he will intersect with the spits flat turn (where he pulls the trigger and boom!).