In my carreer I used twice the speed brakes to increase fuel flow thus my weight, you just need 1/8 of speed brake, which is not a lot.
Was this during cruise?
What do you think about using speedbrakes (Flight detent) against power, during a non precision approach? (Before the procedure turn, but a few miles before the IAF and during outbound too)
Approach based on a VOR/DME located at the airport
Thanks