I've had a gorrilapod in the bag for years for just this purpose and it works fine, mainly gets used for taking timer photo's of me and the misses when there is nobody else around. I've not got a quick release as it's so quick to screw on and it happily handles my 5D mkii and Tamorn 28-75mm f2.8.
I've tried the bean bag/rucksack appraoch and the gorrilapod always produces better results with a lot less fuss plus it gan be used on all sorts of other ojects from trees to fence posts. I have a lovely set of the sun setting over Uluru taken with the gamera on the gorrilapod perched ontop of a slope topped post.