425mm chainstays should make it a manual machine!
I know it's not a trail bike but 680mm bars just seems so narrow to me now. I don't think I'd like anything less than 760 on any bike!
It's all relative isn't it!
The 26" BMX I've been riding has 390mm chain stays, and I have to say it's noticeably easier to initiate a manual compared to the Saracen. Both are of course much easier than a 440mm+ chain stay trail bike!
I also think BB drop seems very important to how a bike feels to manual - the Saracen has quite a high BB and I feel like maybe this is offsetting the slightly longer chain stays and keeping it easy to get the front up.
You're dead right, 680mm feels so narrow now
I think my ideal on this sort of bike is probably more like 720mm, but I like that Tioga stem so much I think I'm happy to stick with the bars I've got, they actually feel fine once you get over the initial "how narrow is this" moment.
I love my 780mm bars on my trail bike, but having watched videos of myself I do wonder if I should try going a little narrower... The wide bars are great for monster trucking through chunk but I do think they limit mobility somewhat.
I feel like the more it's about the rider's input versus the capability of the bike (and modern FS bikes are very, very capable!), the more sense a slightly narrower bar makes. Still wouldn't want to go below 720mm on rough & steep stuff though.