Well, after reading this thread about 3 hours ago, jsut out of curiosity I folded the curtains of the room with the 'stat up onto the windowsill. Then had to close down that rad. as the temperature in this room had stabilised about 0.5C lower than usual (it's now back to its previous value. The curtains so folded are between the top and fins of the type 11 rad., with most of the pleats against the wall, so it seems to make some difference. This is a very small sample!