Curious, when you are rolling each bike around, is the hand on the bar furthest away farther on the 750 versus the 550? If so, me thinkin' that comes into play as well.
Are y'all trying to roll them straight up or at an angle, resting on the side of your keister? I have to roll my Venture at an angle, resting on the side of my keister. Straight up scares the shiite outta me. Me thinkin' it will fall over. Those bars are much wider apart than the 750 too.