I dive a conventional set up and have dived DIR which i find uncomfortable. I am a larger sized fella and i guess the long hoses can wrap tighter for me than others.
anyway I dive mostly with my GF who is familiar with the conventional set up. hence we use the following.
apeks balanced primary 2nd stage on necklace
apeks egress octo on right chest D ring. The Octo is mounted on a bungee cord that is pull free in emergency.
it is best in my opinion that you and your buddy are clear with each others set ups. Keep it simple just in case
i like diving with necklace as i hate fishing around with my arm to find my primary.
haha. safe and happy diving