[Dusk Blue Z]

Rubber works as an insulator, you can touch the hose when the engine is hot but you don’t want to touch the radiator shell which is down stream.

I took a look at your pictures, I wouldn’t put tape on the housing on that car. Just measure the thermostat housing with the thermometer close to it. The cooling wind from the fan and the built in error factor in your tester I don’t think will change your readings enough to worry about.

Mike