Fermentation Lock Luck

I pitched the yeast Tuesday morning, and finally today on Thursday I was able to place the fermentation lock on. This seems to be a very active batch, but I also noticed it got off to a slow start. I tried to place the lock on last night but failed miserably. foam was spouting all over the place, into the lock itself, and repeatedly popping the 7 1/2 cm stopper out of the neck. I tried with the same stopper today and still the same, so I tried the 8 cm and it worked the first time. I actually don't know if those are centimeters, but I do know that 8 is bigger than 7 1/2. Note: get another 8 for a two carboy situation.

Hope I didn't contaminate anything having it open for as long as I did, jamming in a rubber stopper over and over with my washed but still human hands.