Swapping to BBB but what about CalHypo

[chem geek]

As a rule of thumb, for every 10 ppm of FC added by trichlor you are also adding 9 ppm of CYA and with dichlor every 10 ppm FC added adds 6 ppm CYA

This is a typo and is reversed. For every 10 ppm FC added by Trichlor it increases CYA by 6 ppm. For every 10 ppm FC added by Dichlor it increases CYA by 9 ppm. Between Trichlor and Dichlor, it is the latter that raises CYA more quickly.