One thing that you might want to consider, is.....more biomedia does not always mean better biofiltration.
Benificial bacteria don't increase just because there is more media.
The benificial bacterial population ebbs and flows with the amount a food available, from the output of the fish, if there is enough media.
Of course you could have too little space for colonies to live on, but .....once the bacterial population hits equilibriums with ammonia and nitrite output of the fish and other metabolism going on in the tank, it remains stable.
If you did a test for ammonia and nitrite with half the media in the sump, you might find half would do the job as well as that entire pile.
But only your testing can determine that, with the amount of stock , and your routine.
I would agree its always better to have extra media in case your fish spawn, or you add new fish, or they grow, but....cramming so much that flow is reduced does not always equate to better.
Remember, over time every inch of glass, every rock, all substrate has the potential to be covered in beneficial biofilm.
