The balance won’t be too far off.
Option 1: Linearize the K4 (warm) master curve first, then you can mix the linearized cool and linearized warm curves to make a neutral curve that won’t need linearizing.
Option 2: Mix the master K4 (not linearized) with the K5 curve to make a neutral curve and then linearize just the neutral curve. This option does not properly linearize your K4 master curve so it’s not the best approach.
cheers (and glad to see you on this forum!)
Walker