Tuning the tesla coil

I've completely constructed the tesla coil, and now I'm at the hardest stage of all, tuning it. To be honest, it's even harder than I thought. I succeeded in measuring the frequency of the primary and secondary coils. The primary seems to be around 700-800kHz, while the second around 1,1mHz. However, when I add a toroid-like dish or something to the secondary, it's frequency drops since I'm increasing the capacitance. The two frequencies almost match, but it still keeps giving me sparks of around 50kV, i.e. 5-6cm long. This is not how it's supposed to be... The coils are both very close to meet the same resonance, but there is still something that prevents the sparks from reaching long distances. One reason might be, that I'm using a fly-back transformer from an old TV. I'm using a 555 timer and power N-Mos transistor, to drive the transformer (there are more components, but they are irrelevant in this case, so I'm not going to mention them now). I also reduced the turns in the primary coil of the transformer and added a diode rectifier. So overall I get roughly 5kV, which is reasonable. Anyways, the spark gap is very well construced, I've made it, so that it can be easily adjusted with a screws. What I've noticed, is even if both of the 5nF, 6kV capacitors are connected in series, giving me a 2,5nF, 12kV capacitor, it still takes alot of time to fill up (judging from the slow frequency of the spark gap switching). I think thats also a reason, why my TC still gives me such weak sparks. One thing I might do, is increase the frequency of the flyback transformer, that will increase the current, therefore the capacitor will fill up more quickly. But then there's a chance that the transistor might blow (not that I didn't blow up 6-7 IRF730 transistors already, still wondering how this one is kept in one piece). Another reason for this awful appearence, might be that I'm using 28 gauge wire for the secondary coil (i.e. around 0.3mm). In the end I might be forced to rewind the secondary coil with thicker wire of around 27 gauge. Too many considerations, but I have alot of time, I'll do whatever is necessary for my TC to work. So, if you have any suggestions, share them with me, that may ease my work greatly :)