So I'm sold on trying a shorter stem length. I'll be coming off a 105(have always felt stretched) what size should I go to. I was thinking 50 or 60 by what I've seen on you tube

Man that's a tough one.
Always great when you guess right the first time. Doesn't always happen though.
Coming from a 105, I'd try a 70mm first, before I went any shorter. 

Plenty of shops will let you try a different stem or two out in the parking lot to help you decide.

Well, 105 to 70mm will be a radical change that you'll notice.

I had one bike that came with a 75. I put a 60 on it and it felt all wrong. I replaced it with a 70mm and that was the sweet spot for that particular bike. What handles best on tech features, wont necessarily be the best for climbing and vice versa. So, it's sort of a compromise. 

One general rule of thumb is, if you're on the bike in attack position, look down through the handlebar and see where the handlebar is in relation to the front axle? If it's in front of the front axle you need shorter stem to get it to line up, if its behind then you need a longer stem. You can do some rough measurements with a tape measure then convert to mm or go to a shop and hold different stems up until you find the right length. It's not perfect, but it's a good starting point.

Another option is to get a bike shop and get the bike fitted. Costs a few bucks, but once you do it you're done. I think the Cycle Path does this.

As I said before, the cheapest option is once you get a general idea of the right stem measurement, try a different sized stem or two from the bike shop or borrow one or two from guys here. Then buy the one you want.

I've got a basic bontrager 90mm I will loan/give you that I won't miss. 

Like the others have said its a bad idea to swing for the fences with much more then a 10mm change on stems all at once. 
You mention kitsuma and I'd say you'll appreciate the shorter more so on the DH then whatever it might do for you on a climbing switchback.  When all line choices are equal I find it best to swing wider rather cutting hard in the switch back but your mileage may vary.
Pm if you want to hook up and try the 90mm.

720mm is considered short. What is considered long nowadays? Do y'all have banged up knuckles

OEM spec logic: I'll give you 800s and you can cut them to whatever you want

when I bought my bike, 680's were considered wide. Backsweeps were a big thing also. So are backsweeps still a thing. What about riser bars? Or Jones bar's?

Zakaraia Hermes wrote on 03/12/18 at 2:16pm:

ENVEous

Zakaraia Hermes wrote on 03/12/18 at 2:16pm:

trails are wider then when I was a kid

Zakaraia Hermes wrote on 03/12/18 at 2:16pm:


I ride 720's on all my bikes. And on some trails around these parts, it's a snug fit, even without trying to squeeze by a bike going in the other direction.

I've been riding trails on bicycles since the 1960's.