Obviously I am not Mike or Larry, but ......
Can you save a photo and give us a link so we can see it? That can make a huge difference. Because we don't know what shape you are using, that in itself can make all he difference in the world. Do you get any action at faster speed? Is this a copy of an existing lure or a new design of your own.
Remember what Larry posted on his videos, the three factors that make a lure work.....Center of Gravity, Control Surfaces, Buoyancy. Depending on the lure, any one of those three may be the most important.
https://www.youtube.com/watch?v=ZaZAiWG ... u.be&rel=0https://www.youtube.com/watch?v=CJXuGqe ... u.be&rel=0The method you used can, if properly done, place the center of gravity low, which helps a lot in this type of bait, if the control surfaces are correct. The superplastic on top, with Microballons, is great, if you have enough Microballons. Try dropping the lure in a picture full of water and see if the weighted portion sinks down, and the bait self rights quickly. This is important for this type of bait.
Seeing the picture, with hooks in place, will help a lot in guessing if the center of gravity is in line with the line tie, an important factor in this type of lure.
So many factors can come into play. I have a lure that swims fantastic, if properly weighted, but won't swim at all if I get the ballast off by even a little. It goes from hero to zero so very quickly. I have other designs that almost work no matter what. It can take a long time to troubleshoot a new bait, and every piece of the puzzle helps us figure out the big picture.
Hopefully you can get us more pieces of the puzzle to look at so we can try to see the big picture.
Good luck,
Steve