CCS/DRV8305-Q1: F28069M and DRV8305-Q1EVM: Current Monitoring via MOSFET RDS(ON), how it InstaSPIN compensate RDS(ON) with temp?

Tool/software: Code Composer Studio

After a bit of reading and watching teaching motor some trick training video (which is very good, but dated since VisSim no longer supported). 

I'm familiar with RS observer that correct RS (shaft winding resistance) over temp.

I found having 3 x sense resistor can be a bulky choice for the small board, so I like to try using RDS(ON) but they vary with a temperature between -20C to 125C + self-heating (MOSFET).

Should I be concern about this? and how to limit the impacts of RDS(ON) variation?, does instaSPIN has a feature to account RDS(ON) variation, where I can find details?

I may consider using DRV8323 or DRV8353. 

R.