use the stock tail mount because it is stiffer than the gws fin tail that tower sells (and it's already installed). to fit the 12mm diameter motor, round out the flat forward portion where the motor goes. i did this using only a 1/4" cylinder diamond grit bit on my dremel tool. it doesn't weaken the mount enough to make any difference. i'd also leave the bearing housing alone in case you'll ever want to use a gear drive tail later on. if you don't think you'll ever use a gear tail again, you could chop the bearing tube off to save weight. otherwise just remove the bearings and keep them in a safe place.
for DD: the motor mounts on the left of the boom, prop on the right of the boom, with the prop lettering facing left.
the high voltage gws DD ("X") motor is rated for 7.4V continuous and the battery is 11.1V, but on the blade's tail you'll only be using 40% power most of the time. so they last a while.
as far as the brushless tails go: the equipment by itself costs roughly $75 and requires a programmable radio (which new are roughly $200+). also the power of a brushless tail is unecessary unless you have a brushless main to compensate for (which is another $75-$90). by then, your blade will also accellerate in every direction much faster than stock, which means you'll have more expensive crashes and more of them unless you have hovering mastered.
besides investing in extra batteries, i'd honestly say upgrading to the brushed DD motor is the only other upgrade worth the $$$ from the start with a cp pro. when you find yourself outflying the heli (which takes some aggressive lines to do), start digging deeper into the hobby starting with a heading hold gyro. when that gets old buy a brushless main. then, when you need more start saving to buy a programmable tx, with intent to use it as a gateway to a trex. then give the cp a brushless tail to top it all off. j/k you don't need to take me too seriously, there are many ways to invest in the hobby. the important thing is that you're having fun with it (and aren't going broke either).
