DONT BUY THE F10. Stay far far away. exactly as mentioned above, there has to be atleast as much mods put into it as the kit itself costs to get it to handle more than a 21.5t.
My reccomendation, Buy the Exotek F104 conversion and pull up a F104 manual and start ordering the parts needed to complete it(replace the factory parts with the hop up versions.) will save much time and money.