Max Extrusion speed with 0.5mm nozzle

I wonder if somebody could share some printing speeds when using a 0.5 mm nozzle.
I am printing with a Felix 3.0 printer. The problem i have is that i print a box with walls 1.4mm thick, so i set extrusion to 1.4mm and 0.2mm layer height. Printing PLA @190c.
The first 30-40 minutes are fine, and then the extruder starts skipping steps.
I print at 40 mm/s which means roughly 11 mm3/s volume. Same happened on 30mm/s speed. When i reduced the speed to 20 mm/s the print when fine with the wall exactly 1.4 mm thick. Which is ~ 5mm3/s

Then i tried extruding 100mm fillament in free air at 12, 10, 8, 6, 5 mm3/s. And in fact only at 5mm3/s and 190c, i could extrude exactly 100mm. In all other cases there were 3-5 mm underextrusion (that is - only 95 mm fillament went in).
I could extrude well ~10mm3/s only on 210c.

Those numbers are fine for me, but i kind of assumed that 10mm3/s is the nominal for a 0.4mm nozzle, and a 0.5mm would go better.

It would be great if someone could share some numbers
Thanks!

Everything in the extruder-chain from the spool holder to the design of the nozzle can play a part. I am not familiar with your printer so, if your extruder can not build enough pressure, the hot end not melt the filament fast enough or something else is the cause is hard to say. The make and even the color of the filament can make a difference.
5 mm3/s sounds a bit on the low side but it is only meaningful to compare with a identical setup. Try drop the question to Felixusa.
280% execution width might be a bit on the high side.

That is almost three times the nozzle width - far too wide IMHO.
Try two at 0.7mm wide and your extruder won't choke.
Keep in mind the filament needs to be transported AND it needs to heat up properly.
There is always a compromise between the possible max speeds you can print over the quality.
And if you over-extrude like that I am quite sure you are also on the limits of the slicer in terms of calculating proper values.

Thank you both for the hints, i will give it a try indeed with thinner extrusion.
I chose 1.4 because i have an usb hole in the wall, and this way the quality seemed best.. as this way the wall is only one line wide