You could do that...

Or, you can cut away the doublers that the firewall will be up against equadistancely (is that a word??)

Meaning, if you want a 1/2 inch move back....then take a 1/2 inch off the doublers. Make the cuts before you glue and it will be leaps and bounds easier. This will also preserve your thrust angles.

This is all assuming there's enough room up front to allow for this. I'm not sure what's laid our for your fuel tank support, landing gear support, etc. You'll need to think about all this first.