Using a 9:1 compression ratio motor under a Maggie is just nuts. Throwing power and efficiency away. You don't have two turbos worth of boost to play with. You are limited by how much air it's capable of moving efficiently. You'll need an 8 or 10 rib pulley setup to make as much as the guy with 10.7 cr makes with a stock 6 rib. Those big rib set ups are expensive and can eat front end accessories too.
You'll pass a few more fuel stops with the higher cr too. An LS3 powered Camaro gets 5 more mpg than its ZL1 sibling. Almost the same 376 cubic inch engine. Before you mention that the supercharger is the reason for the lower mpg, know that the charger is just along for the ride during fuel eco tests. It consumes less power than your a/c compressor when not in boost. The reason for the lower mpg is the lower compression ratio plain and simple.