I believe the old exploit of dropping a tanning tub in a boat to pop it to 92% is gone.
That said, I've had a tub in and around my house and found it to be quite glitchy. Brought the tub in and out of the house, left the house when it was in and went into the house when it was out... ended up glitching back to that good 'ole 92% again.
Funny thing is, I took it out of my house and left it outside. While I was outside with it, it progressed to 97%. Went into my house and came out again and it fell back to 94%. I've never seen this before so I'd figure I'd throw it to the community to resolve. I'll attempt to recreate both the 92% glitch and the loss of % glitch to see if I can narrow down the conditions some.