Power down will overcome a too small valve but still might restrict it some. Any restriction below pump flow will slow it down.
Do you know who the manufacture is for your pump? Can you read the tag for specs, like flow? Most are KTI but not all.
They are all slow, aggravating. I am very happy with the performance of mine now. Night and day. I still have to check down speed with a partial load. I checked it with a full load from about 2" up, it drops too fast, hit hard.
I think I will be okay since the load has shifted to the rear after a partial dump.