The company name may have changed a few times but a Cherokee 6 has been flogging to and from Brampton Island for more than 10 years with the fuel police in the Ausjet ops manual. One fuel starvation ditching in 10 years, don't think the policy is the problem.
About 20 litres was kept in each main tank which works out to be your fixed reserve. Why keep fixed reserve in the mains? So each tank always has enough fuel in it to get you safely airborne if you mistakenly select the wrong tank for takeoff. Run a tip dry select a main and you will always have about 20 minutes of fuel to get yourself sorted out.
Short distance, multi sector days with short turn arounds in an aircraft with 4 fuel tanks requires careful fuel tank management. Don't rush,record fuel remaining in EACH tank on the fuel log(not just the total) and visually confirm fuel remaining in each tank on every turn around.