They're not even 10% safe.. and they wouldn't even look good, as you'd only have a bit of flame visible out of the holes- though I suppose the tin could start glowing red hot if you had enough fuel (or silly enough fuel) in there, as it's only very thin metal..
I'm mainly posting in case someone comes across that who doesn't realise that it is not a decent budget alternative to good bought (or home made) fire poi and tries it.. Also, we have had one or two people recently who seemed to be posting on here with seemingly the sole idea of persuading someone else to play with their incredibly dangerous idea, and film it..
Sorry, but making fire poi by filling a tin can full of kevlar (or newspaper), punching holes in the side of it then setting it alight is an idea that shouldn't be so much 'thrown out there' as 'thrown away and never mentioned again'..
My first attempt at making fire poi was dangerous enough.. I tried to wire kevlar rope (that being all I had) onto the outside of a steel core, which was badly tied onto a chain. It didn't work, it was liable to fall to bits at any minute, and I never tried to use them lit..