beat length and beaming problem

[Paul Malcolm]

I have the following (perhaps trivial) but interesting problem. 
I would like to manually set the beat length (for beaming purposes) inside a 
\times n/m {} construction. 
The music is 2/4 time and I need groupings of two sextuplets on the 1/4 note beat. 
Ordinarily 


\times 4/6 {c16 c c c c c}


But I would like the beaming to group this sextuplet as a collection of three groups of two, 
not one group of 6. 


I have tried using the beatLength variable but Ive either misunderstood how it works or 
am doing something quite wrong. 
This is what I tried, 


\autoBeamOff
\set subdivideBeams = ##t
\set beatLenegth = #(ly:make-moment 2 16)
\times 4/6 {c16 c c c c c}


Perhaps manually setting the beatLength inside a \times n/m 
needs special consideration ? 


Paul