You might research this, though it most/ALL likely will alter the sound somewhat (see link).
Do you have backlight showing through folds/ridges on the cone (I'm experiencing this on my favorite pair of vintage paper cone drivers and I will probably try a light "directed" application of Puzzle Coat)?
Please describe the weakness you perceive.
https://www.t-linespeakers.org/design/tweeks.html
DeKay