Does anyone know whether the sail kit will? And, if so, are the needed padeyes etc already on the hardshell hulls or will I need to obtain and mount some?

You must have a specialized inflatable sailkit with stays. The hardshell kayaks (and new inflatables) do not use stays. I think there is another difference in how the inflatable mast breaks down into 4 sections. You might give it a try without removing the stays, because they may turn out useful. I vaguely seem to recall the infl. sailkit can substitute for regular sailkit without the furling option, but not sure.