Maximizing overhang using 2×4 furring installed over monopoly framed house – GreenBuildingAdvisor

Zone 5b, 50 psf ground snowload. Attached is a simple drawing.

I have 2×4 furring  over 5″ rockwool on a “monopoly” framed house, I want to use the 2×4 furring to add the  overhang, but how much overhang can I reasonably leave?  It will get 1×4 furring at 18″oc in a grid on top of the 2x4s.

I left them long so I can snap a line and cut them back, but I’m having trouble finding any info on adding overhangs this way.  

Any thoughts / ideas?