I used the hex-bar included with the HPMX kit for a while. Couldn't get full throttle out of the setup without wacky accelerator cable angles. Linkage developed slop rather quickly as well. Ordered the CSP bellcrank linkage through Rob, and boom. Awesome.
I would recommend ordering the extra return spring they sell as well, but otherwise zero issues. Easy to setup, easy to adjust and (imho), better looking.
-Dave