Thanks for the tip, I have size 8's lying around and they would not fit in the bottles so I was forced to use a #7. At this point I believe there is a small amount of CO2 in the bottles and they were pushed up due to lack of headspace. I don't think I'll sweat it until I see one explode. I have about 300 crown caps that would relieve the headspace situation if necessary. Do crown caps preserve wine well?