Just a thought (take it or leave it): Should probably be higher than 1000 because the max supply of this coin is much higher than other coins that do 1000 collateral.  Maybe 2000-5000 range is right.

Of course, there are counterarguments, like maybe you want to be a coin less focused on ROI and more focused on raw # of masternodes.  I'll leave it to you guys to decide.