Without a "brake booster" type of brace, centerpulls mounted front-facing will tend to toe out in response to increasing lever force as the pivot posts splay apart.

Another problem with centerpulls, as with canti's, is that many of them require a lot of skill to get the pads adjusted to the right angles on each axis.
The pads need to meet the rim oriented straight after the gripping and friction forces have pre-loaded the freeplay out of the pivots, no small task with an amateur mechanic having to adjust 4 pads!

I and others have made these "bridging" braces for front centerpulls, this one of my own design: