How are you measuring the durometer values?
What Shore test are you using and are you doing it by hand or with a test stand? If you aren't using a good Shore D durometer with a test stand, you values will vary wildly and not give very accurate results.
I'm just using a little Shore D digital for $60 on eBay.
Testing by hand works fine for what I'm doing.
If I was selling tips based on the actual test vs. manufacturer, then I would get more sophisticated.
For instance years ago someone gave me a box of 15mm Lepro tips.
We started testing them and most test close to 80, which is great for a Lepro.
People love these, but I don't use Lepro period, I've been giving them away to my local tip-ferrule installer roommate.