There is an amazing trick you can try. You will need feeler gauge or maybe a set of washers ranging from super thin to a few mm in thickness. This works best with rdms but can work on sdms too.
Follow Rogers first procedure 1, 2, 3. In stage 3, when the mast is bent there will be a slight gap between the upper and lower section. Insert a feeler gauge that just fits this gap. Release the mast. The gauge will sort of get stuck when the mast flexes back. Now twist the mast 180 degrees so that the place where the feeler guage is is up. Press the mast down again. The thickness of the inserted feeler gauge will create a leverage that pushes the mast halves ever slow slightly apart. The best thing is now to have an extra set of feeler gauages (or to take it apart) since you will repeat the process and insert a new gauge in the gap that gets created on the underside when you bend the mast.
Repeat. When you have created a gap of ca 2mm, you will likely be able to twist it apart manually.
I've had mast that 8 people with booms couldn't get separated that I later managed to separate myself with the above method.