Obviously playing 8th notes from the 16th notes is a easier way out, but keeping up and tight with the 16th notes in a thrash guitar riff involves high coordination with your 3rd finger (ring), and if you can.. your 4th! (pinky, little finger) so your doing a 3 or 4 right handed finger technique..

Im sure a lot of the bassists here can familiarize with the bassist Alex Webster and his technique in keeping up with a lot of the guitar riffs in Cannibal Corpse, he uses the 3 fingered technique.

Hope this helps,

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