Just purchased a 2016 superlow and wanting to fit up some pullback t bars but can't with the in built risers has anyone had luck with switching out either the upper or the complete triple tree for something else? 

You can easily remove the risers.  There's one bolt holding each riser to the top triple tree.  Much easier than messing with the triple trees themselves.  Most t-bars I've seen replace the risers.  The stem of the bars connects directly to the top triple tree clamp.  Your main concern would re-attaching the speedo assembly.  I've seen that done by attaching the speedo to the top of the headlight brow.

Sorry OlChestnut, but your comment that the risers are removable applies to all of the sportsters except the 48 and the Superlow. The 48 and the Superlow have the lower riser integrated (i.e. cast) into the upper triple tree. The 48 and Superlow run the "mid-glide" front end with wider spacing of the forks compared to most other Sportsters which have the narrow glide triple trees which have removable risers. I would suggest the only option is replacement mid glide triple trees, or maybe just the upper tree?

Ah, that's good to know.  I didn't think the Superlow used those.