Getting my new orange 5 next week, any advice on what chainstay protector to use? I was looking at the endura one as they do a medium and large but not sure what size to get.

Old inner tube and a couple of zip-ties. Universal fitting.

you don't need one. the paint is very durable. I've done about 600 miles on mine with flat pedals on, so my foot does scuff the chain-stay. its not marked yet. plus protectors look crap.

Lizard skin protector. Does the job and looks ok.

I've got a Lizard skin 'swing arm'protector on mine and fits perfect.

Just put some sticky velcro on the underside, does the job and does not spoil the look of the rear end

not pretty but it works ,its called an Endura swingarm chainstay guard