I found a workaround for the issue 
By commenting out line 195 to 199 in the Source Code of
Engine\Plugins\PCG\Source\PCG\Private\Elements\PCGCreatePointsGrid.cpp
and recompiling the Engine i was able to tell the Engine to skip the check for Physical RAM and use as much as there is avalable + Pagefile.
Caution: obviously by using the Pagefile instead of RAM the process becomes very slow.
Feature request: A checkbox in the PCG Plugin settings for “experimentally ignore memory restrictions” and set the code in line 195 to 199 to not execute if checkbox is set to true.
So there would be no need to recompile the Engine 