Internal Channels are undersized too?

[Quark]

You might want to play with horizontal compensation in the S3D settings. You may be able to tweak for the tolerance you want.

I'm not using S3d for this, but wouldn't that setting just give me thinner walls altogether? My walls are good at 3mm +- 0.1mm.

Not exactly - this is the thread I always go to when I am trying to remember how to use it

https://forum.simplify3d.com/viewtopic.php?f=8&t=2965

so yeah, exactly how I thought it worked. The channel is coming out at 6.5mm where it should be 7mm. Since the channel has two horizontal walls between it, using the horizontal compensation to get it to 7mm means I would enter in a negative .25mm. This effectively takes away .25mm of all solid surfaces, enlarging my spacing to 7mm, but also shrinking my wall thickness by .5mm (.25mm on each surface). The channel there is empty space, and not accounted for in a slicer. This is an additive process so it only cares about what is physically there, basically surface layers and anything in between them. Maybe I still misunderstood that setting? I attached a picture for reference on the channel spacing I'm referring too.