Hi,
I have a great deal of experience with Metatrader as I trade forex for the past 7 years. I have to say optimising was always something I loved doing tweaking to the very last bit of performance.
Reaching a 99% model quality for the past 6 months depends on two factors the tick data but also the EA programming. if you're unable to reach such quality for your backtesting we can take a look at the programming behind it to see where it can be improved.
If you got any question or for guidance in other Metatrader project you may have feel free to contact me, it would be a preasure to discuss with a fellow Forex trader.
Best regards,
Andy