Shift of CurrentRanger range to piko-ampere range

[Henning]

I need to measure currents in my setup as small as few hundreds of piko amperes, equivalent to fractions of a millivolt if the nano ampere range is selected. I'd therefore be curious whether it is possible to shift the dynamic range of the CurrentRanger by one (better two) orders of magnitude towards low currents, to get better precision.
Is there a way to modify the Currentranger accordingly?
Could one achieve that by replacing the reference resistors, i.e., from {10 kOhm, 10 Ohm, 10 mOhm} to {100 kOhm, 100 Ohm, 100 mOhm} (or even {1 MOhm, 1 kOhm, 1 Ohm})?
Anything I'm missing?
Where is the limit?
Your thoughts are appreciated!

[Felix]

Theoretically that should work. Although I haven't tried something like that and therefore I can't warrant it.
If you shift by a single decade you will have to reinterpret the readings accordingly, or modify the firmware.
Not sure about noise figures but surely that will increase. And if you experiment with this you'd want good quality resistors.