This is what I got. It's pretty straight forward i think, also worked well for my waspish, and troiar, though haven't checked with any other bots.

speed= [rbs*(1+nLvL*0.03)+(rm-(lwf/100)*rm)*0.02]-SUM(mass) *0.02

rbs- robot base speed
nLvL - navigation extension level
rm - robot mass without any eq or modification
SUM(mass)- it's the mass of all your equipment without the robot
lwf- lwf % modifier 20% = 20

If it's incorrect feel free to correct it:)

Have fun!