My advice on this personally would be to use one of these three:
Powerpacker (latest version you can find)
Imploder 4.0
Titanics Cruncher
All of these crunch nicely and in my experience are system friendly so you know your one file demo is going to work OK - as long as you've coded it to be as friendly as possible itself that is.
If you're crunching for demo type stuff where you don't care about the system at all then you could do worse than Photon's cruncher available from the Scoopex website as there's docs and a decrunch source too.
By the way, DP - if you want any of the ones I mentioned I can send them to you - just shout.