Gentlemen,
I had an electric hardtop hoist for my 450SL for several years, but always hated the roof-rack styled method of securing it to the gutter rail. I was never really comfortable with its security.
I wanted something better for my 250SL but could not find a commercial product that I liked, so I made one. Total cost ended up at just over $200.
The hoist itself is a standard Ebay 250kg electric hoist. - $185.
A couple of meters of 500kg seat belt webbing - $15
Weather Seal Guard and load spreader – 3D printed – virtually free
It took a couple of goes at getting the seal guard to be rock solid and able to transfer all the loads to the chrome trim and avoided any contact with the weather strip.
In use, there is a secondary backup strap (not shown in these pictures) secured to the rafters for safety, as the hardtop is suspended above my 2007 SL350.
Works a treat.