Hi, and welcome to the forum...
How many? How long? Any straight portion? When you say upper die I'm guessing there's also a lower die? What sort of circularity do you expect or require? I'm not seeing where you'd need any springs?
There's more than one way to skin a cat. Lot depends on quantity, quality, finish dimensions and any further processing that the part might go through...?
Right off I think if it's jsut a couple / few pieces or a hundred even... and you can stand some slight ripples just whip up a custom (for your radius requirement) conduit bender. If it's a few and you'd rather no ripples conduit bender and pack the tube with sand or flour etc. and cap it then trim after the bend. If there are a bunch of these then do a search "tubing bender" and either buy or build a bender with a mandrel and wiper block set-up. You're not going to need much oomph to move the part.
More info and might be more help.