The OEM inner rocker had 2 reliefs pressed into them that are approx. 1/4" wide and 1/8"-3/16"" deep that were used to allow any moisture that entered rocker to drain out. The current extended outer cab floors that have the inner rocker built onto it have these reliefs on them. So I'd recommend pressing the same reliefs into your inner rockers.
here's a photo of the extended outer cab floors that show the reliefs I'm talking about
Now if you don't keep these holes cleaned out along with door weep holes then door bottoms and outer & inner rockers rust out once debris clogs them and they begin to hold moist debris.
Paul Jr @ GMCPauls