Having trouble with Cura 5.1 not detecting a bridge

[FTsabrovAS 0]

Hello all,

 

I'm trying to create a geometry that can be printed support free over a square nut or over thin air. I've made what is in the attached image, with two layers intended to bridge the gap before printing the hole above. I intended for this geometry to be a bridge, but Cura 5.1 is not detecting it as such. Is there something I'm doing wrong?

 

Default bridge settings turned on

~8mm wide square hole

~5mm wide round hole

0.15mm "steps", same as my layer height

0.4mm nozzle on my S5

[FTsabrovAS 0]

Did some more experimenting- the bridge is detected if I increase the bridge skin support threshold from the default 50% to a whopping 95%. I suppose it is counting the surface area overhanging relative to the surface area of the previous layer, not just localized to the overhang. I suppose this works for the piece I am printing now, but is there a downside to keeping this value this high?