Wouldn't worry about it.

If it works for you, it works for you. Doesn't matter that it's generally not a good filter, and doesn't have the capability Sta-Rite claimed . . . since it obviously has the capability to do YOUR pool well!

But, to answer your question, the problem is the design, not Sta-Rite's cartridge construction techniques. An aftermarket filter can't fix the faulty design.

Again, the problem is that the filter was designed in such a way that StaRite could CLAIM much more capacity than the filter actually has, after it's operated for a little while. But, in lightly loaded situations like your pool, it can function just fine.

Ben