I have 2 ultra vac's. One is a two bag on a trivantage deck and the other is the 3 bag on the ultracut deck. The statement above is correct. If they do clog most of the time it is right where the deck meets the boot of the vac. Impeller will just keep spinning not hurting the belt at all. Ultra vac's are very nice. But I have clogged the units especially the 2 bag many times. Usually in wet conditons. They are very easy to take on and off when you get it down. Around 30 to 45 sec.I don't OWN one, but I did demo one a couple years back. What I found is that even if you plug it up, it pluged at the boot between the deck and the blower fan and didnt' actually impair the fan from spinning.
I'm hoping to be able to demo another, with the Triton deck, sometime this spring. (the one before had the older trivantage deck)