I know it's mainly trial and error. I don't think there's any danger in moving the jack plate up and down the full range while running fast. But for trim, how do you know when you're trimming up too much? I'm sure it becomes obvious at some point, but how do you know when you've trimmed as far as safely possible? I have a Ranger Z20 with a Yamaha 225. I can only get it to about 50mph by GPS. My boat guy (who is well-respected and trusted her on TFF) cleaned the engine, changed filters, separator, good compression, etc and said he got it up around 64mph. Thoughts?