As mae-ling said, its a slider so theres no issue with swing. I am going to shoot for enough overlap to cover the sealing groove (see below)
This isnt exactly what ive got, but it shows the basic profile..ish. Bottom right cutaway, top and bottom right corners there is a square pocket (im assuming for calking) So Im going to plan on my jams covering that, I dont mind a step, so as long as that groove is covered, I think I'll be happy with it.
While Im on the subject, should I use any sealant on the interior between the Jam and the vinyl frame? I was thinking just to keep the jam from having any sort of gap agains that edge i might use some white silicone or something...its tight on the exterior so im not worried about weather/infiltration...just aesthetics..