We use Bubblegum tags on Hebs, Shetlands and Soay. They're not especially small but they are soft and bendy. We don't put them in to newborns though - we mark those with something tiny like a turkey wing tag, which doesn't leave a mark behind when it is removed to be replaced with a permanent tag at 4 months.
If a tag does tear out, use Superglue to repair it immediately (it was developed for wound closure in battlefield situations and only later used for sticking everything else.)
We have found that certain sheep are more likely to pull tags out - the ones which stick their heads through mesh fences. Hebs grow out of it once their horns grow a bit, but Shetlands can often still get their heads through in adulthood.
I agree that positioning of the tag in the ear is important, but will add that we have found that having the loop at the top reduces tearing - but then others have found quite the opposite