Dave took the words right outta my mouth, but I'd also like to add that you might want to extend your welt all the way to the mouth of the sheath. It appears your retention is mainly taken on by the handle. Imaging holding that knife between your fingers at the fingertips, then grab it with your whole hand, much stiffer.
I use a Loveless cam when I need a little more than just molded retention, beware though, one of them done with a little more height than needed can totally refuse to let the knife seat. I have a wood carving tool that I use to fine tune the cam.