It sounds like you have done something to get your beater to hit the middle of the head. But what?

Raised the drum?

Shortened the shaft of the beater?

Got a Jacques Capelle (or similar) pedal?

If you raised the drum try lowering it a little so the beater hits a little above the center. Experiment with how much to lower it.

If you shortened the shaft of the beater this causes lots of flow on changes. Consider lengthening the beater and letting it hit above center. If you can't get an improvement, consider lifting the drum.

If you want to try a port I've heard good things about the kickport, but haven't tried them myself (I use an on the floor 18" bass with calf heads so kickport is not in my paradigm).

What sort of beater are you using anyway? wood? hard plastic? soft felt? That makes a difference.

It might be useful to share a few photos with us as well as complete specs for your kick. Does it have wooden hoops or metal rims post conversion, for example. What pedal do you have? What heads are you using? It feels like we are having to play 20 questions to get enough information here.

There hasn't been much discussion about heads. A 16" drum is going to have much more kickback than a larger drum. A 16" head has less than 2/3 of surface area of a 20 inch drum and keeping the tension up for that Bop sound will make the smaller head rebound pretty quickly. A thicker resonant head tuned as low as you can go will help and a double ply batter head will as well.

The closest drum I have to yours is a 14" King BopCat and I'm trying to get it lower----I am using an Emperor X as a batter, mostly, and experimenting with heavy skin heads( moose-bear-older cow-bison; I have access to these skins and get them custom tanned for me as whole hides). With heads of this nature , the rebound is very controlled. The drum is on a riser, with a full beater shaft swing and hitting dead centre. I also use a skin(calf or goat), beater patch.

I have never tried it but I always thought a fullgrain(about 1/8") leather beater patch might be of value , rather than rawhide. In your case, it might cushion the beater slightly, disturbing the kickback ----in a similar way to using a softer beater but wouldn't deaden the " bop" sound so much??? I apply these things moist with crazy glue and some pressure under a flat plate and weight. Crazy glue reacts to water and bonds with it.