We can leave it as it is too, I'm not too sure if the Sanskrit letter 'ज्ञो' from यज्ञोपवीतम् sounds more like the English 'gyo', 'gno', 'jyo' or 'jno'!!
Ref: How to rename a tag?
OK, I took care of it. See here.
I think "Yagnopavitam" is better than "Yajnopavitam", because usually we spell the word for Vedic rituals as "Yagna" rather than "Yajna" in English. On the other hand, we usually write the word for knowledge as "Jnana" rather than "Gnana". Ah, the wonders of transliteration!