I’m planning a 3/12 mono pitch shed roof on a new house build in southeast BC Canada zone 6 with the following inside to outside. 
-exposed 4×12 fir rafters 24”-32” oc- terminated at wall plane aka monopoly framing 
-3/4” T&G plywood sheathing
-ice and water shield as WRB
-3 layers 2.75” reclaimed fibreglass faced Polyiso insulation with lapped joints 
-2×4 horizontal strapping with 12” GRK or similar fastened directly into rafters
-prolok standing seam metal roof

Questions –
1. Should I have a layer of felt or other above or below my 2×4 strapping? Does the fibreglass felt like covering serve a similar function? 

2. Is there a need for vertical 2×4 strapping first to provide some ventilation and would this negate the need for felt if included?

3. I plan to install roof overhang “outriggers” on top of the sheathing/wrb layer bolted directly into each rafter. these would be “L” shaped 5.5” in depth on insulated part of roof and raise to 8.25” on overhang. This would allow a full layer of 2.75” Polyiso to lay on top to mostly eliminate thermal bridging but would incur an energy penalty. besides structural considerations (will add bolt on knee braces or use LVLs etc if needed) are there other concerns or good alternatives anyone can suggest to achieving deep (3’-4’) overhangs? 

*note will be building perfect walls as well with 2 layers of Polyiso over framing.