I have a custom cover fits pretty tight. I usually tow with it on for security and protection. There is some flapping or movement near the back causing minor rub marks in the gel. Maybe back cover air vents would cure this. Also leaves a dark area where it rubs the coated headers at the top bend...polishes out. Any movement can also wear the cover over time. The ends of my headers eventually cut through the cover...even with extra material in those places.
That said, the cover's 14 years old. All things considered, not bad. I've towed it covered coast-to-coast and countless trips to the lake...so it's a trade-off. If your gel's flawless and you want to keep it that way, then I'd say no. Hard to keep dust out of the fabric leaving some rub marks. But I like the security of nothing seen during stops along the way, and the protection from rain, bugs and road debris.
jer