Guttentag Rhein Rader wie geht's, I am also one of the pilots that is often requesting a lower level in stead of flying the filed Flightlevel. In our company the flightplans are generated by LIDO and since we are now flying with winglets, the optimum flightlevels are more or less the maximum flight levels if we would follow FMC predictions. The problem is that everything what is filed, is based on weight and balance assumptions and unfortunately these assumptions are often wrong. In many cases we are a lot heavier than predicted and also the weight distribution is different. Let alone that the computer is calculating ISA atmospheric circumstances. Which are often not the case. Especially in july it was a lot hotter than standard in Europe. Last but not least the computer generated flight plan does not take in to account CAT or turbulence from TS, where I do in order not to fly in the ''coffin-corner'' while more than light turbulence can be expected.
Danke und viel spass,
QTA!