Diamond Flash Questions (No, not the Usual Ones...)

[pkmgarf]

So, after using a few different ROMS on my CDMA Diamond (Mighty, Energy, Juicy, etc), nothing really does exactly what I want it to do, so I'm looking in to cooking my own (BuildOS updating right now).

That said, my goal is a clean, fast WM6.5 (Titanium only, TF3D doesn't really impress me) ROM with only the necessary apps (no GPS, etc).

My questions is this, do I really need to flash my Diamond back to stock before flashing new ROMS to it? I've read a few places that it is recommended. If so, why is it necessary? Shouldn't reflashing overwrite any/all values that flashing to stock would change?

If I do need to go back to stock, I would have to undo Hard SPL, correct?