No expert in this specific type of print, but:

I’m sure you already have, but: make sure your calibrations are perfect, of course. Esp volumetric speed, but also I highly recommend adaptive pressure advance calibration. Prolly not gonna help here, but worth it anyway.

Given the height, is it possible to design 2 2d walls offset by .1 - .2mm? That way it’s sandwiched between 2 walls. Kind of like the gap a vertical support gives, but this is horizontal. The (sandwich) bread walls, if you will, need to be thicker so that as you add vertical height it acts as the support. That’s the only thing I can think of. Printing such a tall / thin object unsupported in any way feels super hard. Also maybe could just do vertical towers of support vs doing a ton more filament for a full sandwich.