is it possible to use fuel cell foam on the robots doesnt say much about it in the manual



Not as a structural component, it may qualify as a non-structural decoration as such it cannot touch game elements or the field.

Basically no.

You can use squishier foam like this though. Comes in 1" widths too so may not be what you are lookign for. It is in the catalog.

You can also order adhesive foam from the vex website