I did a Foto for you!!
So here you can see my Bike and Cranksetup.
It's a Profile Magnutanium with 145mm Crankarmlength and with a 5.5 inch Spindle inside,
on a Zion Focus Frame. I use this setup of Cranks with Tree-Spline-Sprockets for years now and was using it on a lot of other Frames ( DIV, Instrumental, Collier, Quamen, MikeS Frame............)
in different BB-Setups and was always fine fine with it. There never was a problem with Framedents from Crankarms or something like this.
If i would use a 6 inch Spindle it would be to long cause i would have to take the Crankarms much more outside without any needful effect for it. So if you ride a Garuda you will not have any reasons to use a 6 inch Spindle.
As you would take Crankarms with 175mm lenght you could think about the Idea of using a longer Spindle.
But if you use short ones like 145mm or 160mm there is no reasen for it.