Shoe clips?

Hi everyone,
I really need to wear flat shoes under my wedding dress. I've looked at some online shops and they offer beautiful shoe clips to add a bit of bling. Two questions...
1, Can they be trusted to stay on the shoe?2, Will they irritate the top of the foot?I'm trying really hard to find a shoe that won't leave me uncomfortable or cause me to keep fussing! Many thanks for your responses.