I use a Breville single loaf bread maker semi closed, Bosch 630 heat gun, DMM bought from Andy.
I successfully roast 725g in one batch every seven or 8 days.
Re your questions,
"can I go to 600g (500g roasted) with an open cover?" perhaps, give it a try.
"What's a good base profile in terms of timing? How long til FC and then til SC?" depends on your set up and heat gun settings.