Thanks Arthur,
I am a bird photographer, the walking is a great bonus. Your reply has prompted me to look a little further. I have the Tamron lens and for that matter the 750D as well.

I went down this road to improve my photos, in particular more frames per second. I also have a Canon 400 prime. Bit shaky and Mr Magoo like. One thought I had was to use the either the 750d or the 7D with the Tamron and the 400.

I really hate giving up, I might tune up with the 750 for a couple of days then switch to the 7D with those two lenses.

Possibly a better sling set up and a way to distribute the weight.

Thank you very much for your help,
Kind regards, Journeyman