There are no strict spelling rules in Egyptian writing. In the place of spelling stood aesthetics.
Beauty as a Rule for Spelling: Whatever spelling looks right is correct. Aesthetic considerations are almost the only limit to the different ways in which hieroglyphic text can be written, and that includes even the direction of the writing.
To note, Egyptian writing in the Middle Kingdom contained about 700 signs (no one has counted them exactly), which could sometimes have more than 1 meaning. The writing was taught by whole-word method rathen than phonetically.
:)