Good point, the slew drives so have a hole through the middle. Depending on the size, it may not pass a 3" pipe through the middle or 3" may be undersized, but I'm sure the same idea scales to larger and smaller sizes.
Hey, I am not criticizing your project. I am just showing the cost of a tracker off the shelf ready to be assembled so that people can have a comparison. As you said, your project was more of a hobby than a saving cost project, and the learning from your son is invaluable.
By the way, those channels can be cut, and the tracker can be bolted to cement, but I am just testing the location before doing something more permanent.. and that wood base is currently anchored so the wolfs cannot blow it.