Lets say that one game will be 50 min and you will double up a minimum of 60% of the time.And you are a grinder ♦.
Lets say that the limit is 1+0.10$ STT.And you get rakeback 30% flat +20% from the 100% FDB => 50% rake
One day 10h(pure grind) 
6tables ; 10h ; 72 games ; 7,2 $ win ; 7,2 $ rake ; 3,6 $ RB ; =>
10.8$ total + ; 0,15 $ + per game or 1.08$/h(don t troll for calculating penny limits win rate
) - in the period of FDP clearing with 50% RB lets say 30 days.
If you play 20 of those 30 days whit this volume and win ratio you get:
200h ; 1440 games ; 144 $ win ; 144 $ rake ; 72 $ RB ; 216 $ total + ;
So if you start with 80 $ and yuo double up 60% of 1440 games you will profit $216.And your BR will be 296 $ thats 3.7 times growth.
Edit:Well I am still not sure plz correct me in time so that I don't misslead somebody
Last edit: All the math was made in 20 min with pen and paper....
♦