the space between the slats are 9mm, always a thought IanY, but you could buy some of that real fine mesh and lay it between grill and case/rad.

Should still allow for minimum back pressure and protection from little fingers.

I remember once when I was little, my parents took us to one of those Holiday camps and we had this entertainer entertaining all the young children inc me.

For some reason when near the stage I decided to stick my finger in the hole that created the smoke, lets say I never did that again after the burn it gave me.