just treated myself to a think tank glass limo backpack ,there are very few bags on the market that will take the sigma 150-600 sport with lens hood fitted ,this is one of them with the added advantages that it will still take a couple of other lenses and some accessories and without a weight penalty as it weighs in at 1.5kg empty .
i have tried lots of other bags and they all are lacking in one form or another this seems to fit the bill nicely .90% of the time it will be empty but if like the other week a sudden shower comes up at least i can keep camera and lens dry within a couple of minutes .
other large bags i have had in the past seem to suffer from initial heavy bag weight and then being cavernous you tend to cram everything in .impossible with this so its just the wanted stuff