Most of the HRDx's I have seen that are working fine, have not had many if any modifications. Not to say that the ones I have seen that work well haven't, but ......
The truth seems t be that they are like people. Some are good, some are ok, but have some issues, and the other half or so seem to be pretty bad in general, occasionally doing good, but then back to there regular bad ol' self!
Really though, the ones that work well do so quite well........
The ones that don't , welll.........you get it.