With the apparent speed cap ( which I disagree with for this reason ), you won't have any need to max blitz fist and thunder.
Your weapons will get you beyond max speed easily without blitz fist when using thunder.
Thunder is basically being killed by this cap..
If that's the case, you better off spending that SP on buffs or debuffs.
*signs petition against speed cap, signs petition to prevent karma & poko speed buff stacking instead*