I ran my D215 on Friday with the hydraulic plate for the first time. I used to have the fixed plate off the transom. They are the same width but the fixed plate is 1" longer. There was a pretty dramatic difference in shape when playing with the hydraulics.
Top speed was best with the plate at about 25% which is up most of the way. Launch was best at 100% which is all the way down. I could steepen the ramp at speeds from 8 to 25 easily by putting the plate up and could make it less intimidating for my kids by putting it way down. I didn't notice much difference between 0 and 25% unless I was going really slow. The hull did not porpoise with the plate at any setting.
We had whitecaps and rough water for a while and the boat ran best with the plate at about 80% or at 0% when I was going slower than planing speed.
This is the hydraulic adjustable plate. (I've always wanted adjustable attitude in boats)
and this is the Barefoot fixed plate. (It came on my boat)
By the way, the Sanger handled the chop better than my old 18' I/O would have. I'll wait for a big storm to tell you if it's as good on really large rollers.