We purchased our Sling 2 months ago & ordered our top at the same time. We're located in south east Florida and put about 1200 miles in topless. For us a top was an absolute must as the Florida sun beats the snot out of you.
We installed the top a week ago and have 400 miles of drive time in. In my opinion the top was built really well & love the way it looks. The "t's" pop up easily for getting in and out as well as come off completely although we have not attempted to do that as of yet. The frame itself is solid and welded quite well. As far as the sun beating down on you and the accompanying heat issue, completely solved, mission accomplished! We have been caught in a couple light rain showers and the top definitely helps a bit with that as well.
We also have a wind restrictor on her so we had to change that to a front mount (no big deal). With our particular setup of the double bubble shields we have created a new issue. The wind now deflects right into the top/cockpit and the restrictor creating massive wind and turbulence (wearing a hat is not possible). So now it's time to buy a new full shield that sits a bit higher which is no big deal.
The wife and I are quite happy with it! I couldn't find much if any information on the Gull prior to purchase so if anyone has any questions feel free.