Yeah this things are really unpredictable. You inspired me to post some indoor funny videos. I am updating them in my thread.

great Job man!

did you calibarate each ESC individual? 

ya bro...
i saw your video... coz of indistinct view... i m nt ble to make out ur esc...

but wit my ss 18 amp...
i m nt able to completely synchronize all three... there is always 19-20...
well at first till 20%throttle almost 1 motor is off...

but at around 50-60... when it is about to take off... all motor moves as espected...

while take off need to balance it manualy by giving ail/ele a bit...

which mode r u using on tx?
try using areoplane mode..

and while on ground during take off first give 20-25% throttle... and then balance movement by moving ail/elel stick...

i mean to say if your tail motor is going slow... give elevator front.... same wit ali.

not sure...
but in my case... it is balanced...
n flies smooth..

first try
trim..
mode to airplane (it should not matter, but it worked)
balancing by sricks...

gudluck