https://terrylove.com/forums/index.php?search/2180024/&q=thomas&o=date&c[title_only]=1
might be of some help
Here's an addendum to this thread:
https://terrylove.com/forums/index....ons-quattro-flushing-technology-toilet.23750/
Can you see the poor engineering? Too loosen or replace the hold down bolts you have to remove the tank to loosen the flush valve, rotate it, then you have access to the bolt heads. To install the tank you first install the hold down bolts, then install the flush valve, then tighten the flush valve wrench (good luck getting a good purchase with the bolts sticking up in the way), then drop the tank down onto the bowl, then tighten the nuts. Obviously you only need to install the left bolt and washer before installing the flush valve over it before tightening the flush valve nut. Dollars to donuts that that will be the bolt that you can't remove...
The problem won't surface now, it will surface in a few years after the bolts have become rusty or mineralized to the point that you can't get a thick straight edged screw driver blade to hold the face of the bolt as you try to un-tighten the nut. Since you won't be able to hold the bolt head with the screw driver, turning a wrench from underneath will mean the whole bolt will turn. Which will mean that you will need to saw it off from between the bowl and the tank. Hopefully you will have enough clearance to be able to affect a sawing action within a confined space. If you cannot get a saw blade between the tank and bowl then chances are you will need to either saw, file or Dremel the nut away. And if you can't reach those nuts then you will need to pull the whole toilet off.
And why would you need to get get access to those bolts and nuts? If the rubber washers harden and break, causing a leak, if the toilet needs to be removed for re-modelling or painting, if the flush valve tube cracks, if the coupling gasket starts to leak because too many people who sat on the seat leaned too far back, causing the tank to move forward and back so many times that you get a leak.
Tip: before tightening the nuts, apply some Plumber's Pure Silicone to the bolt threads, closest to the nut ultimate tightening area, so that it will be easier to remove years from now.