"Turning 'downwind' in a constant airmass with a fixed angle of bank is going to have the same performance impact as turning with the same angle of bank in a non-moving airmass"
Please consider this as I have witnessed this many times. Ie holding in very strong winds.
I reduced angle of bank to prevent excessive IAS loss.
Ground speed heading west is IAS minus wind. ( the Perth Westerly, sea breeze can be quite strong in high temperature days)
Ground speed heading east is IAS plus wind.
Inertia must be increased quickly therefore IAS will drop until ground speed equals IAS plus wind.
Sometimes this requires over a 50 knot increase in a short time.