2003, we converted a 1996 Ford CF8000 commercial truck to our concept of an ExpeditionVehicle.
We use 3010 (three feet wide by a foot tall) dual-pane sliders designed for a stand-still house.
We mounted these at our eye-level standing inside, about eight feet above pavement.
For the sealer/adhesive, we used Vulcum 116.
Nearly two decades full-time live-aboard.
Twenty-four months twenty-four thousand miles around South America.
Alaska, Panama, all over North and Central America.
The Vulcum 116 remains soft and pliable.
re -- silicone chalk
Semi-retired welder-fabricator here.
The squeeze-tube stuff you use around the tub in a stand-still house would be my NEVER choice.
Based on a half-century of camping in lesser rigs, experimenting with all kinds of combinations of components and chemicals, silicone chalk has zero-zero-zero stretch.
On a vehicle with each component constantly shifting, silicone chalk breaks, then requires a second application, then a fifteenth.
After a wet night with leaks everyplace, the silicone chalk must be removed so something appropriate can be applied.
Although silicone chalk fails at its primary mission of bridging gaps, it manages to adhere admirably.
* you start with a putty-knife,
* quickly graduate to a chisel,
* by the third week -- family long-gone and the neighbors concerned for your mental health -- you are considering the nuclear option.
Trust me on this.