Can you install custom kernels on DroidX running CyanogenMod? Can you install custom kernels on DroidX running CyanogenMod?

Or does the locked bootloader prevent that?
No, The DroidX can not run custom kernels.

"It is still impossible to flash custom kernels on the Droid X, but the ROM developer community has matured to a point where they’re able to make great things happen on this phone without having to rely on changes to the kernel."