Sorry I can't be of assistance (no experience), but impossible?
Every frame is intact (well almost) and originally intended to run in 24fps. PAL just plays it erroneously fast, there must be authoring programs that can correct this and convert it to BD(24p). (or will converting distort it unacceptably?)
Anyway reason I want BD 24 is mostly the audio pitch-up of 25, but also why watch films incorrect when there's a choise.