Bumping it up to 500 would be ok.
What's the cube root rule?
Quite simply, it's the cube root of the entire US population. I'm not sure why, but it seems to be a common measure for ideal representation in a national legislature. In any event, it works out quite well. If it were used from the start, the House would have grown by 12-32 members each decade (the smallest growth during the 1930s and the largest during the 1950s). Based on the 2010 Census, the House would currently be at 676 members, an increase of 21 from 2000's 655 members. Also, based on current projections, the House would increase to 694 in 2020. I think an added benefit is that an ever-increasing House such as that would remove the zero-sum game that apportionment brings about (although it would still be possible for states to lose representation).
The Wyoming Rule isn't bad as a number for the current population, but it's quite unstable when you have the smallest state growing more rapidly than the nation as a whole. The current House would be 542, but that would have dropped from 568 in 2000. For most of this country's history, had that been used, there would have been huge shifts in the House (from 1308 in 1890 to 1862 in 1900 to 1095 in 1910). Yes, the House would have had two consecutive increases of more than 500 members before dropping over 700 in the following Census.
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