What version of Ultra Hal are you running?
On Ultra Hal version 4.5, you had to write special .uhp files to make the .htr Haptek files work properly. Just like you, I never could write them to work properly for some reason, and for experimental purposes, I did exactly the same thing as you... I renamed the desired files using existing character names.
The good news is that Hal 5 writes the .uhp files automatically for you! If you put a valid, working Haptek character into the "Characters" folder with the proper .htr file extension, Hal 5 will generate all the necessary support files the first time that it "finds" your new character! Your character appears and works with very little muss or fuss!
You do, of course, have to make sure that you have a good, functioning character with a legitimate .htr file extension. My version of People Putty directly outputs characters with the correct extension, and all is well. However, I have heard other People Putty customers state that their software outputs unusual file extensions such as .hap (or something) and they had to experiment and change file extensions to get a good, working .htr file.
In my opinion, the automatic recognition and support-file generation in Hal 5 makes it worth the switch to the new revision!