Recently I've seen some of Harlequin's birding shots and looking at the settings, I was quite shocked.
600mm+1.4TC at 1/90s handheld. Shots were sharp to say the least. Was thinking and this set-up probably weighs at least 8 kilos with the body included.
Was hoping some of the bird shooters who regularly pull off shots with such settings could share some of their techniques so users of smaller glass(like myself) can apply it to concert shooting and other low light situations.