You can add a DWORD registry setting at HKEY_LOCAL_MACHINE\SOFTWARE\devnz\RingBufferSize. This is a number of bytes, so the largest you can specify is 4GB.
Obviously for a DWORD the max is, as you say, 4GB, but for reference for anyone setting it, 4GB does NOT mean 40000000000, it's a little over... The MAX value you can possibly enter (for that near third of a gig! is:
4294967295 (or ffffffff in hex)
Is there any plans to make this more flexible? I have a 200GB hdd and don't mind having a 15GB pause buffer for example, in case a REALLY insistant salesman comes to my door... Oh God I hope not! 4GB is fine, just asking out of curiousity, not naggiosity!