taxi time at LEPA/PMI is 15min, after a "perfect" transit you should call ATC 15min before yr slot...if you call 7min before ATC is entitled to refuse you...maybe you say "we are able in 7 min to take-off"...but are you sure about how many other aa/cc were taxing at the same time??
I'm a flight dispatcher/ops controller, still trying to make pilots aware that slot means take-off time and not off-block time...
Ciao
Paolo