UV Unwrap large cylinder produces distorted UV

I can’t UV unwrap a large cylinder (50m radius, 200m high, 360 vertices) - the top/bottom cap have a weird distortion. I’m using “Mesh: Mark Seam” on the top/bottom rim and one edge on the side. (There’s a “UV: Mark Seam” - one of these is from an Addon maybe?)

A regular cylinder (1mx2m default) works fine. Also tried 50x100 x 180verts - ok too!

Any ideas? Thanks!

Change the UV unwrap method from the default ‘Angle Based’ to ‘Conformal’ when unwrapping

Thank you! Perfect!