Sheldon's recommendation is probably ok but I wouldn't leave a full length 300 mm steerer on, say. a 50 cm frame with a 100 mm headtube. It would look, and maybe act, too much like a spear!

Also, Sheldon's technique would require a BIG stack of spacers, at least temporarily, to set the headset adjustment before tightening the pinch-bolt collar to lock the adjustment in place.