Piano Centered Dynamics

[Tim Hucker]

I'm engraving a piece using Lilypond 2.4.2 under XP using the template in
the 2.4 manual
"3.3.4 Piano centered dynamics" on p32.

I would also like to align non-dynamic instructions (e.g. rallentando, a
tempo, perdendosi) between the staves but cannot for the life of me work out
if is it possible to use the dynamics context for non-dynamic instructions.
If so how do I do it?
If not how do I change it so that I can?
If I can't change it, what's the best way of aligning both sets of
instructions?

If anyone has had this problem before and can suggest a solution I'd be very
grateful for help & advice.

Regards

Tim