Split SFF File with Bioconductor Package

I need to split a big SFF file into a number of small SFF files.
I was able to read in the big SFF file as a big SFFContainer with the function readSFF in the Bioconductor
package:R453Plus1Toolbox. I also fond the index to split the big SFFContainer. For example, the index
(5,11,17,22,25,29,31,33,37) for the first small SFFContainer.
I couldn't figure out how to extract the (5,11,17,22,25,29,31,33,37)th reads from the big SSFContainer
and construct a small SFFContainer and save it as an SFF file. Could you please tell me how to do this part of work?
Thank you very much in advance.

Heidi

 -- output of sessionInfo(): 

> sessionInfo()
R version 2.15.1 (2012-06-22)
Platform: x86_64-pc-mingw32/x64 (64-bit)

locale:
[1] LC_COLLATE=English_United States.1252 
[2] LC_CTYPE=English_United States.1252   
[3] LC_MONETARY=English_United States.1252
[4] LC_NUMERIC=C                          
[5] LC_TIME=English_United States.1252    

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base    

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