Vase mode seems like the way to go, tbh. Don’t waste time & material on infill.
What I would do is create a model in TinkerCAD. Make a sketch, fill the volume, clip a corner to avoid the exclusion zone, raise to your height target, then export the STL and print as a vase. Here’s an example:
I added notches to the sides to add rigidity:
raise to 250mm (or whatever your target is):
bring into Bambu Studio, enable vase mode, set bottom shell layers to 0 (in the Strength tab, not shown here), and add a small brim to keep it in place:
You also can modify the printer settings to ignore the exclusion zone, documented in the link above. (I didn’t bother because I am not actually going to print this test.)
This is huge, yeah, but it gets the print head near all edges, so if something is wrong at a specific spot you’ll probably be able to spot it. To be more thorough, disable the exclusion zone and don’t notch the corner.
If all you want to check are the corners, then maybe just make some 20x20 cubes, stick them at the corners, and make them as tall as needed.