I want to change the mid-range and top speed of the model.  It has the generic decoder common with the locos that are DCC Onboard.  Usually the two CV's related to those two characteristics are CV5 and CV6.  Literature with the loco did not cover the CV's in the decoder.  Searching the Backmann website, so info for the generic decoder was found, but it did not contain any information about CV5 or CV6.  I get the idea that these two characteristics may not be changed in the decoder.  Is that true?  Does anyone know if these two CV's control the mid-range and top speeds, or can they be controlled in another location in the decoder?

Helping a friend with a N scale H-16-44 diesel item no. 61456.  Literature with model shows some things about DCC but does not identify candidate decoders.  Which one should I use Mr. Bach Man?