Re: Too big keikogi
Do your pants not have a cord? Or are they the elastic waist kind?
Either way, I would never use a safety pin or anything with metal or with sharp parts. I guess it depends on how you train in your individual dojo, but I would feel very unsafe with anything like that so close to me when I'm training.
Must be some way to either sew them smaller or use a cord of some kind to tighten them.
Or see if you can find someone bigger who needs a new gi to sell your gi to at a discount and get part of the money back to buy a new one.