I'm late to the thread, but considering adding the IBS. One issue I have is when my locker bag is full, the locker lid doesn't close completely. I have to drain the sac a bit for it to close. How does this affect the front sac? I suppose you just wait until the IBS is filled, then hit the empty switch so the lid will close?

Also, how do you know when to stop filling the IBS? Do the front cushions pop up or do you have the timers set for the whole setup?