I concur. Mixing of headset races is challenging. It can change the loading angle on the balls dramatically, and consequently affect performance and life span. It is best to assemble then disassemble and compare the tracks in the grease with the original race. If the track is very high or low on the race, then it is likely not a compatible fit, though you should always compare the angle of the tangents to the track.

I've always found soda cans to be too soft for shim material. It is a satisfactory temporary fix but the race eventually becomes loose again. My preferred material is a steel feeler gauge cut to size. The advantage, besides the harder material, is that you can almost always obtain the exact thickness required and most automotive supply houses have 12" lengths that they sell as single units.