My sparkling mead did not sparkle!

I have a problem that i'm kind of upset about and was hoping someone could offer some help. I've made sparkling mead a few times with pasture champagne yeast with excellent results. However, it always came out a little on the dry side and too alchoholic for my taste. So for my last two batches i decided to switch yeasts for a change. I used a montrachet yeast with 16 lbs of honey in a 6 gallon batch. i let it ferment and bulk age for 4 months racking twice, and then bottled it with 8 oz of corn sugar to prime. i let it condition in the bottle for 6 months before deciding to try it. when i finally did crack one open i was very dissapointed, the mead tasted wonderful but was almost FLAT! It had only the smallest hint of sparkle. So my questions are where did i go wrong and how can i fix it? i'm unhappy enough with the result that i would be willing to open all the bottles, dump them back into the bucket and do some work on it. Thanks in advance for your help.

Any suggestions on how to fix this particular batch besides buying an entire kegging system? I was thinking about opening the bottles, dumping them into a bucket, repitching with champagne yeast, and immediately rebottling. Do you think this would work?