You can spell it however you want. You can pronounce it however you want. You can have it mean whatever you want.Wrong! it's spelled like it sounds, YUNS! who would know?
If you want to communicate with others, however, they need to know what you mean. Following at least some of the rules of the existing language is advisable.
Is the word a contraction of two existing English words? Is it a compressed version of a longer word?