So andropenis (manufacturer i bought from) have this 9 hour plan. I told them i can only do 6 hours per day and worked out if i need to add 0.5cm after 7 days of 9 hours i can instead add that same amount but 6 hours per day for 10.5 days.
On other websites i just hear people talking about you should wear it for 2 hours, 4 then 6 to get used to it... not the length of the device and adding rods. They said to me you don't need to adjust the springs or anything.