I find it interesting that many posts on MFK are from people with hard, high pH water that want to keep soft water, low pH South Americans.
You are just the opposite, you have water the above aquarists could only pray for, yet you want a cichlid that loves hard, high pH water.
I live in the area this Parachromis comes from.
The rain here has a pH of 8.2, some of the lakes attain a seasonal pH of 9.
That said, I believe those Parachromis will adapt to your water, if not, you will find out later, if HITH becomes chronic.
The suggestion of using crushed coral (aragonite sand), or crushed oyster shell as substrate is right on the money, it will help buffer the pH, and calcium content and keep pH from crashing in low alkalinity, and doing lots of water changes and filter cleaning to remove metabolic acids before they become problematic, will help.
One other filter technique I used to keep pH up, was to run a DIY fluidized bed reactor with fine aragonite sand as media. As the aragonite slowly dissolved I was able to regularly add more to maintain stablility from its open top (commercial ones are usually sealed).
The reactor below.

Water was pumped at enough velocity thru the aragonite to keep it fluidized (constant motion).
The aragonite also acted as bio-media.