I like to cook two slabs of ribs indirect using two Weber charcoal baskets on opposite sides.
A very common set-up.
If I had a 6" high ring, I think I could do 4 slabs laying flat.
With a roto ring, add some bolts where needed to support your second grate.
Cajun won't sell a roto ring with no holes punched and the 12" stacker seems like more than I need.
If I was in charge, I could pull a roto ring off the line with no holes, but alas, I am not in charge.