Slide Drive Possibility?

Our team is considering a slide drive base for this season, however 2 issues come to mind. The first is that the middle wheel may get stuck when we try to traverse the step. The other more prominent issue however is that if we collect boxes in a forklift like mechanism on the front of the robot, the weight would be significantly unbalanced. Would this cause the robot to curve to one direction when carrying a significant number of weights? We considered a counterweight, but as the number of totes being carried at any one time will range from roughly 0 to 4 or 5, any counterweight would be redundant. I ask whether anyone who has used slide before encountered this issue in the past with a weight imbalance hindering their drive train?

EDIT - We were considering having the middle wheel attached onto a piston - has anyone done this before, or know of a reliable way for it to work?

148 used a cylinder to push their center omni wheel down in 2010 to clear the bump. They had nonadrive that year but it will function exactly the same.

148’s 2010 release video (visible @1:10)
148’s 2010 build blog