Actually, not mental at all.. I find I have to do that with my two 21" screens - so I guess a 27" 4K display would actually be a good "compromise" *cough*.

I don't like working on anything larger than 25" (NJ) as Mike pointed out, I don't want to actually move my head when working on something. It's the same for games, I don't really like playing on massive screens, even if I sit far back from it.

I like to huddle infront of the screen all by my self.