So the ISTOY165 kit fits fine in place of the JBL's- apart from the woofer (door speaker) requiring the hole elongated? Did you leave the built in crossovers on the Focal speakers in place- or bypass them? My understanding is the JBL system uses active crossovers so the crossovers on the ISTOY165 shouldn't be required? And you left the stock JBL mid range in the dash?
It's been something I've considered doing for a while for- the same reasons. It just doesn't sound right stock.
Have you left the ANC functioning too- does it still work?
(I've circled the crossover components below.)
View attachment 38135
View attachment 38134