No replies, but lots of views, so I'll post my solution: derived by pure experimentation: SLOWWWWWW

Printer: Rostock Max v2
Filament: Generic Chinese PETG 1.75mm
Bed: 70 C
Nozzle: 245 C, 0.4mm orifice
Layer height: 0.2mm
Perimeters: 4
Infill: 10% honeycomb
Speed: 25mm/sec

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