If you do take the swivel bolts off, the bolts are kind of a star drive. But a 1/2" allen socket works. They can be a bugger to get off. I had to heat them with a propane torch. I leave the bucket on, and bungee it up as far as I can. The last OEM Volvo bellows I used, had hard plastic in the corrugated section. Never seen that before.
for me the hardest part is putting the ground cables back where they belong. Also I used a flexible screw driver with an extension for the clamps. Not sure which method is best . If you can't get the bolts off, try the bungee. Good luck Dave-R