My first big glass and holy hell this thing is HEAVY! Really makes me appreciate the 400 5.6 prime alot more than I used to. I’m not so sure this is something I want to deal with all the time…The RRS mini Ballhead is holding it alright but I’m glad that I didn’t sell the AS B1 now.
You will come to appreciate the option of having the faster glass. So somedays depending on your time/target and light conditions, you grab the f2.8, leave the 400 at home. Other days you grab the 400 and leave the f2.8 at home. Then one day the road, you think it will be a good idea to have a second body..One for the shorter faster lens, one for the longer, lighter lens and lug both
As John has said, some days you just leave it at home. I know some photographers insist on carrying everything they have all of the time, but I can not nor will I try. Just decide what you want to do that day and which lens you want to do it with and leave the others behind. If nothing else, it will force you to learn that lens.
Anytime I pack a 300mm f2.8 of larger lens the tripod and/or monopod goes in the car. While you can shoot some of these superteles handheld it will not take long for you rethink that decision.