SurfaceGuis are not actually designed to adapt mesh stuff, SurfaceGui’s surface and size is based on the Size property of the MeshPart and not on the actual size or surface of the visual model that you see.
This can basically be described like this:
If you create a new default part with the same physical attributes of your MeshPart and put a SurfaceGui inside of it, in theory both SurfaceGuis should appear in the same exact space on your screen.
ScreenGuiTest.rbxl (85.8 KB)
This is the demonstration of the method I explained, you can turn on and off the AwaysOnTop properties for seeing the frames behind them.
And this is a quote from a Roblox Staff member, describing why there is no such thing as ScreenGui’s wrapping the visible surface of a Mesh.