Not that anyone asked but here goes.
Simulation with the 2020 diffuser has finished and its a bit interesting
overall there was a small increase in drag and downforce bringing the cl/cd down by 0.033 and shifting the COP forward 0.026
however, the floor and plank efficiency both rose cl/cd of the floor was up 2.537 and the plank up 5.754
interestingly the floor shifted the downforce rearward by around 0.015 but this was counteracted but an overall increase in lift from the body by 0.026 mainly at the rear.
A couple of images to compare
looking at this it seems to be the top of the floor near the side pods having a larger area of high pressure.
i think i will go back to the 2019 diffuser and continue development from there.
and just a little bit more for those interested in the rear wing here is a cross-section out near the endplates.