Though the original poster never seems to have found a solution,
@TorMag and
@day_trippr made some suggestions that could use some followup...
Because of my TAI, I can no longer picture 3-dimensional models so to try and recover that as well as solve a flow-rate issue, I decided to build a dual-concentric CFC. As part of this, I experimented with trying to devise a way to turn a coiled copper tube into a coiled PEX hose without straightening them out. On my first attempt, I got about 10' of the copper coil into the pex before it jammed....I decided I needed something to help pull it from the pex end while pushing the copper in..Enter: MIG-wire.
Not the weekend warriors flux-core stuff; proper solid wire intended for use with gas. I fed it through the entire lot, twisted and tied one end around a bolt and washer, wrapped the end that came out the pex around a large bolt to use for a handle to pull on and it didn't even threaten to break. With a lot of jerking force and occasional backing up, I got the tube through. Since then it's been my intention to unspiral a faucet-cleaning brush and weave about a 1/4" long section into the middle of some mig wire for an eventual deep-scrub of my CFC. Haven't done it yet, but then I've always been thorough in washing, flushing and occasioanal de-oxidizing routine and I've never experienced a slowdown of flow...probably also helps that I always have a filter stage before anything goes in. Still; the very long brush
can be done, I just haven't had reason too yet....MIG wire will work.

(note: for those who may try and build a CFC themself this way: Don't! For my second coil: I simply took the time to shape the copper coil perfectly with spaces, to the dimensions it
would occupy inside the PEX coil, which I duct-taped into shape and then very simply 'screwed' the copper coil into..felt and sounded a lot like turning a massive snap ring on a pickle jar.
