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It all depends on what you ride really. Imperials are such versatile frames and you can set 'em up with rigid all the way up to an 8" DC forks, some people even go bigger than that.
The 3 different drop out configurations give you three different chainstay lengths, so you can change the geometry, slacken it up and chose forks with different amount of travel depending on what you're riding. Awesome frames and the two split top tubes are fire.
I would do some completely ignorant and juvenile things to get my hands on one of these which coincidently is the appropriate behaviour one should have when riding one. Win/win situation.