Hi Nick,
Your a legend for helping so many people across so many platforms so thank you for all your support and efforts. I have read many of your post on Lift/Gamma/Gain too 
We are just getting into using ACES in our productions and admittingly, I only have a basic understand of it at this point but trying to learn as much as I can.
One question I have lead me to this thread…regarding and better understanding the RRT step:
From what I understand, all incoming sources/images must be transferred into to super wide ACES-2065-1 (uses APO primaries) space before coming into the color corrector. In our case, this will be based on using sRGB primaries in production (unfortunately not ACES CG at this time) delivered to our color corrector (Lustre) via an IDT. In the color corrector, we will work in ACEScc/cct (uses AP1 primaries). When done grading we will then need to render back out to ACES-2065-1 and apply the RRT/ODT for whichever deliverable we are releasing for.
I guess my question here is, does the RRT also use/reference the same AP1 primaries to sort of make sure the images are being processed in the absolute widest real world display “reference” gamut possible before the ODT? Or does this limiting/mapping of gamut happen only once in the ACES cc/cct step (since it too is only working in the AP1 primaries) when your grading in and the final RRT/ODT just maps those values to the appropriate output display where really just the "ODT part of the RRT/ODT combo xform is being applied
I hope that makes sense…
Thank you,
Kyle