When you run a flatfish lure you need to ensure that it is “tuned”. By this people mean that it is running true and not pulling off to either side.
I also include that you are getting the right action – which for this lure is a nice wiggle back and forth.
This tuning process is especially needed if you’ve modified the lure from it’s stock setup.
With the boat in forward motion you want to get the lure submerged and see how it runs. It should have a nice wiggle and not pull off to either side.
If it pulls to either side, then you need to adjust the 2 eye screws. Make sure both the one the hook is attached to, and the one the line is attached to are straight up and down. If it continues to pull to the side then tweak the eye the line is attached to slightly. Rinse, lather and repeat until it runs true.
If it doesn’t wiggle enough, then likely the new hook is too heavy. Going to a smaller hook size will likely fix the problem.
If the wiggle is more aggressive than you want, then upsizing the hook can slow it down.
One thing to remember is that trolling speed also affects that wiggle action. So you need to make sure you are going the right speed when doing this tuning.
What it less obvious is you can use the weight of the hook to adjust the performance envelope of the lure. For example maybe you have times you want to troll faster, and your flatfish will spin instead of wiggle – a larger hook may help balance things out.