The neck you think wouldn't be an issue with bunched fabric? I'm trying to get a year out of the suit before I need to size up. I gained 7 lbs on my body since lockdown so I should have it gone by October.The front looks fine, shoulders, length, and waist look right. I'd take the sleeves up an inch. Hard to tell about the back without a good shot where you aren't twisting to get a decent shot. I'm also a 39 and take a 50 in Ring Jacket. I think it's just a matter of how full you like it, but this looks like it works.
I was worried the buttons in the front looked too strained and the front of rhe jacket wasn't laying right. My shoulders fit well. I'm skinny fat right now though.
Arms feel alright, have to talk to my tailor about trimming them, but with a shirt they fit alright, my hands aren't covered
Edit, fabric isn't pulling at back at all, can hug myself and feel no resistance.