I love my 6x6 system just like you do (not a Hassy, though) so in order to hike with it I radically cut down on photobags/tripod etc. but, more importantly, on non-photo gear. Fewer things, smaller, only lightweight versions, sharply calculated food/drink, multifunctional items. Now I hike lighter than back in the days of my hikes with the small format system!
Regular exercise and enough sleep, help too...
Best, Pete