Tested fully in PLA on my Printrbot Simple Metal black with Printrbot heated bed. Printed with Cura (latest as of july '15). Used the freely available Printrbot config file for Cura, adjusted for 20% fill (possibly even 10%), 1.2mm wall thickness. NO support structures needed. 100% flow. Normal retraction enabled. 210c hotend, 80c heated bed.