991 GTS MA1.03 engine swap to 987 cayman

[slaughter2k]

I am new to this forum. I am dealing the first time with a syvecs system but have arleady some general experiance with aftermarket ECUs (no experiance with DI engines yet).
Topic:
I am setting up a porsche 991 GTS naturally aspirated engine (3.8 liter DI) in an 987. Mechanical stuff is done and working, wiring and electronics are at 80%. Thanks to the Syvecs team I am starting with a 981 3.4 DI base map which is pretty near to the 991 3.8 DI engine. Currently there are 2 big basic questions:

1. Low pressure fuel management: The 991 has a returnless fuel system. The syvecs base map is controling (acc. my understanding) the low pressure fuel pump PWM duty cycle via "fuelDutyPri1" which is coming from a high pressure pump control map (?). Second picture is showing the low pressure fuel pump PWM / rpm map, first picture the "fuelDutyPri1 / rpm" map
--> Is it correct that with this map the low pressure pump would run on 65% duty only?
--> Is my understanding wrong that a returnless fule system should be a closed loop system based on a pressure sensor?
--> I am unsure if the original 991 system has a separate fuel pump controler which is adjusting the pressure to a fixed value, anyway I cannot see the connection in the syvecs map via any CAN signal

2. Displacement and injector size correction: According syvecs team changes has to be made in the fuel map (displacement change) and in the fuel consumption scaler (injector size) which makes totally sense to me.
--> Are there any rules of thumb / experiance / knowledge about the best way to change this maps. Maybe the displacement change of 12% can be roughly calculatet or the size difference of the injectors is known