Regarding SCP 7.10

[htadashi]

#	Description
7.10	Verify that the external keyword is used for functions that can be called externally only to save gas.

Only changing to external will not save gas. The arguments parameters also must be changed from memory to calldata:
https://ethereum.stackexchange.com/a/107939/4630

[damianrusinek]

Thanks for the link, we will have a look on that.