Diameter for ellipses

How we can tag diameter for pipeline with ellipse shape instead of default circular?
E.g. pipeline has dimensions: 650 mm x 1200 mm

For now, I tagged it using multiple value scheme diameter=650;1200, but maybe we already have tagging scheme for ellipses?

I want to avoid using an only smaller value. There are mappers which want to add this data anyway (maybe not a lot), but keeping it in an addition note doesn’t convince me at all.

If they are a pair of numbers of the same thing, elsewhere comma can be used, viz traffic_sign= for a group of signs especially supplementary plates. Semicolon may appear as if for multiple pipes, as how power=line has them.

I would suggest creating new tagging for non-circular objects (possible both a shape and appropriate dimension tags).