I had an atlas as well and I would pretty much leave it around 5-6, then trim up till I just saw that faint spray coming up near the cowling. I think I was around 5775 rpms- or a touch more. I had the 33/10 tank set up. The boat would walk with my 25/3 as well. I never got good at driving it at high speed till I swapped to the 4 blade, and it just ran flat. I feel like on that boat you really have to start controlling it in advance before it walks. Heres a video of me running mine about two years ago. I never realized how much wheel work I was doing till I filmed myself. I ran it up to about 70-71 in that at the end.