Simplify3D not printing concentric infill when asked to.

[DBFIU]

I am printed a tall vase-like structure with 3 shells. I am using concentric infill and it decides to fill it rectilinear, not sure why it is overriding me. This is a huge time waster. Any ideas how to fix that? Thanks in advance.

[DBFIU]

Figured it out, it was the setting on minimum infill for gaps. I increased it to 20% and now it will not default to using rectilinear infill for small gaps. Just saved a whole hour on a 6 hour print job because of this one setting.