I used the coin/level technique to make sure my transducers where level when in the water. I was amazed how much I had to raise up my jack when in the garage to replicate being on the water. Since I run a tiller and sit in the back I can only assume I'm pretty nose high.
Changing chart speed can make quite a difference on how fish appear on 2D sonar. I run around 1-2 notches below the highest speed.