I've never had a problem with observing or even imaging with the scope's weight entirely on the wheels. None of my dollies have screws or any other means of lifting them off the wheels.

When observing from my driveway (the east side of the house), I simply put 2 of the wheels in a seam between concrete slabs and I'm good to go. If I set up in the same place, and roll into the crack from the same direction, I'm automatically polar aligned. But most of my mounts have good polar alignment scopes anyway, so getting aligned only takes a couple minutes each time.

-Tim.