It is true that the thrust force should generally go through the CG, but the vehicle is very forgiving to changes because it is statically stable. The buoyancy foam on top and ballast weights on the bottom mean that the center of buoyancy (CoB) is above the CG, which always creates a force to keep the vehicle upright. When you add additional payload under the vehicle, it moves the CG but it increases the static stability.
When we’ve used the skid, we didn’t change any parameters. If you run into any specific trouble, please let us know and we can advise.
Please let me know if you have any other questions.