Sorry nothing last night... Kids had things to get to.
Anyways it appears I'm ready to eat crow on this one.
I can't explain why Slic3r extruded closer to the set line thickness than cura. However, when i finally got home last night i ran the same print with a different PLA.
Up until then i was printing MG chemicals white PLA. I put in some AMZ3D blue and ran the same print on %100 flow .5mm wall thickness. Object printed with .56 wall thickness. After dialing back the flow to %85 i sliced it twice, one with 85% flow .5mm thickness and the other %85 flow with .4mm thickness.
.5mm file printed with .51 wall thickness, .4mm file printed with .41mm wall thickness. So at first glance it would appear that my initial problems could just be from the filament?