I understand that the addition of a jack plate to a boat will increase performance and economy by allowing the prop to run in "cleaner" water as well as the ease of raising/lowering the motor for proper height. I have seen many adds for jack plates with 5",6",8",10" setbacks. My question is, how do you determine the amount of setback for a particular boat/motor combination. I just ordered a Triton DV 176 Magnum with a Mercury 150 XR6 and would like to have one put on. Any thoughts or ideas would be appreciated.