I know a 200-600 G lens bag survey has been done somewhere, maybe on the facebook page? But Can you fit a Sony FE 100-400mm f/4.5-5.6 GM OSS fitted to a body like the A7 iii or the A7R iv along with the FE 24-105mm f/4 G OSS in a PRVKE 21 litre bag with the medium camera cube. Or would I be looking at the 31 litre bag for travelling? With extras like Bose NC quiet headphones 30 plus a change of clothes and ipad. Along with the usual extras like batteries/leads etc?