I'm trying to laminate a carbon part that's essentially a Y-shaped tube where the outside surface needs to be a dimensionally defined mold surface - inside dimensions don't matter much. Ideally it would be made with prepregs but that's not an option for me at this time so I'm trying to come up with an alternative method. Initially I was planning to make it by wrapping and wet laminating a printed water soluble core and then clamping that between two female molds (also 3d-printed). I have made one project with this method before and it worked surprisingly well but it's a bit tricky to pull off - the main challenge is getting an even laminate thickness so there is compression everywhere while still being able to close the female molds without any carbon being pinched in between them.

So I came up with this idea that's illustrated in the attached image: the soluble core is wrapped in dry fibers and closed inside two female molds. Everything is then placed into a vat of epoxy and vacuum is pulled at the top of the mold hopefully infusing the dry fibers with resin. Would make layup a lot easier  and less messy if it works. Molds breaking during demolding isn't an issue, this would be a one-off part. Has anyone here tried something like this before, is it feasible? I haven't done any infusion work, just wet layup stuff with vacuum bagging, so there might be some problem I'm not seeing. Alternative manufacturing method ideas are welcome too!

Sorry, i misread your post. Light RTM is processed without pressure on the resin, wich is the difference to regular RTM.
Yes, overpressure will be difficult for printed moulds. You could do it, but those moulds would not fit well with the lost plug idea. But you can get good results without pressuring the resin.