oh here is the deal with downward spiral fights...
Its about who travels downward the least. Notice I didn't say slowest, I just said downwards. This is key, there are many ways you can travel downward less than the other guy..
1) You can reduce your downward travel either by making a wider spiral than the other guy
2) Don't blow your 'e' and go down, let him go down and you go up, reverse and then pop him and he can't do anything about it.
3) cut throttle, drop flaps & gear, whatever it takes to fall slower.
4) the list can go on and on..
Remember the guy above, controls the fight, so the most important thing is to try and be the guy above, and don't go down.