Tshan-
Did you note the actual boat in the photo did NOT have that bottom block but clearly a single large ratchet block at the bottom with multiple sheave on top??
Mike used the 10:1 off one of his other boats at the Horn Island Hop and really liked it he told me. Per my understanding the larger the diameter of any block the less the rolling resistance, all other factors equal, so I favor a quad/quint(?) at the top. If going center sheeting can easily make a 2:1 "doubler" system- already have to have stronger boom- but any cascading system will have a set "range" of adjustment- at least at it's maximum purchase.

Kirt