I read the thread now.
Of course the racket head is decelerating at contact. but I still think you should try to accelerate through contact.
many beginners accelerate too jerky and then slow down by contact. that is bad, a gradual acceleration all the way is better.
however it is also bad to accelerate too late. if you approach to contact slowly and then jerk across violently you will not be effective either since that leads to a "pushing" through the ball. you want to hit, not push it.
this is especially pronounced in the baseball swing. elite hitters in baseball generate their batspeed deep in the swing behind the body so that they can be late and still hit a ball hard while mediocre hitters often reach their max. batspeed more than 30 degrees behind contact. that is wasted either as you are not doing anything after the ball leaves the racket.
so you should make sure to reach top speed at contact but not much before.
I would recommend to swing as hard as you can to a point 5-10 inches in front of the ball and then relax and just let the racket fly (no active deceleration).