Help shifting entire tuplet horizontally within a measure

[James Lowe]

Hello,

Here is a snippet

\relative c' { 
    b8.^-
    [ \times 2/10 { c64( d ees d e d c b a b] } 
    a8. a16 a32 a2)
}

I wonder if someone can help me find a way to shit the 10-tuplet over to the 
'left' slightly, or move the group of tuplet-ed notes closer to the first and 
leave the secpnd beamed group (and minim) where they are so that I have more 
space in between and less of a gap between the very first and second note.

I don't really understand how the \override constructs work for the 'grob' (?) 
and have been flailing around a bit in the Internals and the Appendix of the 
Notation so I have tried things like sticking a \once \override...

Beam #'beamlet-default-length = #(x y)

or

Beam #beamlet-max-length-proportion = #(x y)

where x and y are numbers I am playing about with hoping to get something, but 
while I don't get any complains while compiling I cannot seem to shift this 
group over at all.

Thanks for any help.

James