interior questions

Seat back springs....any ideas on how to firm them up? My driverside is a little blown out.

Foam for the bottom cushion what did you guys use i am thinking of 4" piece. it looks like there is 2, 1" pieces on there now

did you guys put any foam in the seat back? if so what kind and how thick

hoping to tackle this job this weekend i have the cover and everything

thanks
justin