@Florence: I think it really sad when you work hours on a piece, let it dry slowly, have ideas for the glazing later etc. and then, only because the studio boss is a bit over-self-confident, the piece breaks in the kiln. And I think it sad that you resign to it. Don't!!
Normally, staking pieces in bisque firings should be ok, if they all are really dry. Also air bubbles aren't always exploding. But heating the kiln too fast over 400°C is definitely a "neck-breaker". I can understand that you like to go to the studio, have companionship, can discuss ideas with other potters, but the price you pay (and I don't mean dollars) is too high. Can't you, for instance, find a few more clay passionate in your area, and you as a group would buy and use a kiln together? Or try to find somebody in your area who maybe has already a kiln in the garage or cellar and would be happy to fire your pieces for a few bucks. Put ads in the supermarket or the local newspaper.