My 1991 Accord SE's radiator mounting seems a bit odd, yet its identical to other Accords that I have seen - why is the top of the radiator not in a fixed position? It is held only loosely in place by two plastic pegs in overly wide circular openings. One can actually grasp the top of the rad and wriggle it a fair bit. Any other car I've owned has the rad bolted firmly in place. Will it do any harm to fix it into a locked position? I'm concerned that the constant shaking can't be great for the radiator.

yeah its normal. honda radiators are held in place at the top by those two round things, but check to see if the rubber is all there. it has like a bushing around it. if not you know you can just change the two things easy.

Thanks for the tip. I think the rubber bushings were indeed a bit worn. I was able to push small rubber rings into the gap, which tightened the fitting while still giving it some freedom of movement.