[plt-scheme] Partitioning Mzscheme Collections

Hi,

I'm currently trying to make a mzscheme package
for my Sharp Zaurusi PDA. I would like to keep 
the mzscheme binary and mandatory libraries
on the in memory filesystem and (more or less)
optional packages on a removable CF-card.

It is not very clear to which collections I need
to have accessible permanently? Could somone 
knowledgeable explain?

Also ist it possible to switch mzscheme into
a "benchmark" mode for faster execution 
(e.g. declare standard R5RS-procedures as
immutable, inline procedures etc.)

Thanks,

/Alex