Doing it in this manner rarely saves time as "dirty" flashing typically causes more issues than the time saving possibility is worth. Same goes for OTA updates. They often cause problems. A reset is always recommended for best results as otherwise it'll be impossible to determine whether it was the install or the rom that is causing trouble. It rarely pays to cut corners in these matters. That being said, just make a nandroid backup and try it. Worst case, it glitches out and you have to re-install the rom the right way.
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