left-aligned dynamics

[James Bailey]

I use the Scheme hack to get dynamics that sound properly with text:
pcantabile = #(
   make-dynamic-script (
    markup #:line (
         #:dynamic "p" #:hspace -1 #:normal-text #:italic ", cantabile"
    )
  )
)

Since I really don't understand any of how that works (I mean, I  
understand that it's markup written in Scheme language, I just don't  
understand the Scheme bits) can someone tell me how to modify this so  
that it's left-aligned, rather than center aligned like normal  
dynamics. I already have a shortcut defined for \once \override  
DynamicText #'direction = #-1, but it would be nice to not have to  
put that in, since every time I use one of these dynamic scripts, I  
want it left-aligned.

Any help is much appreciated.