I need to attach 1-1/2" x 1-1/2" square oak ballisters to the outside of a
1-1/2" x 12" oak stringer (interior open-riser stairs). I'll use a Fuller
drill/countersink to drill the ballisters, predrill the stringer, and use a
Fuller plug cutter for plugs to hide the screws.

I'm looking at the #10 (or #12) x 2-1/2" FSL screws from McFeely's (sq
drive). Are these the best screws for the job (one of the highest torque
values to prevent snapping)? Would #12 be better than the #10's in this
case?

Thanks for any advice,
-Lance