Keslongwood,

The answer seems pretty clear to me. Two filters ARE better than one. In fact, three filters are better than two. Come to think of it, four would be even better. Start with sand, then into a cartridge and then into a DE.

It can be as complex as you like but, simply, more filtration will result in cleaner water. Would I ever do it? Of course not. My pool is crystal clear with a sand filter.

As an aside, I noticed the filtration at one of those huge Ripley's aquariums is sand....I think they had three set up in series.

Now, the real point of my post. I would suggest reading on this forum the experiences people have had with baquacil. You may very well rethink baquacil as your sanitizer. I'm pretty sure others will opine soon....even tho we're sorta' hijacking the thread.