SYMC Upgrade 3.0 to 4.0 - DB Size and Free Disk Space

Finally this Satureday, I will be upgrading SYMC 3.0 to 4.0. Please assist me with following questions.

1) I have only 16GB free space available. SYMC DB size is 8GB. In best practise document, it is recommended to have at least 3 times the space of database size. Now what should I do, there is no chance to have more free space in C: partition.

2) Upgrade is smooth or I may end in a disaster?

I shall follow best practise document for upgrade http://www.symantec.com/business/support/index?pag...