With the sho can stay at 6200-6300 max. The 6000 is for the regular Yamaha. Your speed didn't increase because the prop is slipping still. Turning a new prop that grips will be like a brand new boat in respect to the pitch. You may need a 19 or stay with a 17. It will be trial and error. Go with what works. Tempest, pro series,trophy,fx4 I think, and even the T1 sho prop.
I don't understand what you are talking about with your jack plate heights. You should be able to lower and raise the jack plate a few inches from your "all around" P2P distance. you will want to raise the JP when on place at WOT and lower it to the "all around" height when taking off so you dont even want to be maxed out in up or down travel