Upgrading skills with variable costs

[Nelijal]

Is it allowed to upgrade variable cost skills after play starts, using earned XP? For example, spending 1 XP to upgrade a KS2 to an INT-based KS3, or spending 3 XP to upgrade a CSL5:HTH to a CSL8.

[Steve Long]

Unless your GM forbids it for some reason, absolutely it's allowed.