Well I don't have an awful lot of good to say about the Thunder Tiger .15. I have owned four of them and two I had to send back within the first two weeks due to a cylinder wall peeling and the other blew a rod bearing. Two of them would turn up to 17.5K with 20% nitro and the other two would barely make 17.0K regardless of what fuel you ran in it. But the worse thing wrong with them is the needle valve assembly is junk. The needle valve assembly comes in four parts, the needle valve two washers and a coupling for attaching the fuel tubing. There is no way that this thing will not spew fuel like a garden hose if you try to run it with a bladder tank. If you ever take it apart you will see that the whole assembly when screwed into the carb only catches on about two threads. If you try to put a little pressure on it to tighten it down it will quickly strip out. The aluminum washers will deform the first time it is tighten it down and you will never get them back in the exact same position if you ever dissemble it. The only way that I can keep them from leaking fuel/sucking air is to slather about 1/8th inch of GOOP around the whole assembly and replace the GOOP about every second time that you take it flying. My advice is to save yourself a lot of grief and get rid of the Thunder Tigers and get anything else, preferably OS LA.