I use Hully Rollers. They worked well on my old jeep but the new jeep has a larger spoiler and is more awkward. The rollers still work but I have to use a piece of carpet to protect the spoiler. I’m now considering using a Yakima Showboat. This is a roller that slides out backwards and is attached to the roof rack. It is more expensive but doesn’t require sticking something to clean glass and will work if you have to load two boats side by side. The Sherpak doesn’t look like it would extend far enough sideways to help loading the boat that actually sits over the side of my vehicle. My vehicle is not wide enough to have both boats entirely over the jeep.