[mickmate]

They are about 3/8 gap on the closest points. It is indeed common practice to heat shield them and the master cylinders below them. Stick on reflective thin insulating material is common to wrap the footbox. I have also seen and made reflective shields with an insulating jute type material sandwiched between them and the glass. I have seen fibreglass footboxes about cooked with what looks close to a fire inside with under felt and carpet material.