is that a new engine or old one. those numbers for the APC 16x6 are very low. the Saito 125 on 15% turns 9,000 rpm and is the bench mark prop. maxed out i usally get 9,200-9,300 on 15%
As i said,
the fuel was not new, maybe x3 months old,
so the Nitro content from 15%
may have dropped slightly!