ERich10983 wrote:

same way the spring rate will double. Flip one over so the cones are
opposite and the travel doubles while the spring rate is cut in half.

Doesn't the spring rate stay the same?

Nope. Consider: Spring rate is force change per unit distance. When
you put two springs of the same rate in series, be they Bellville or
coil, each one only moves half as far for a given total displacement.
The delta-F is therefore half.

Ted