so the min drive space requirement is 5GB... then you could use symlinks to another drive if you need to expand your install, or a larger install, so...
... a good question might be what is the recommended size for a full install?
... another question, how many different installs can you have on the same disk, like a 2tb disk, you could partition how many times and not have some sort of corruption? at 5gb you could possibly install 400 times on one 2tb disk?
(my thoughts are that more than 4 partitions per disk is not necessary, so i'm going with an SSD @ 122 GB with 4 partitions around 30GB each; 2 are windows, one xp, other rc 8; 2 are linux, one is mint, the other testing)
if the regular install requires 5GB (presumably some being 'free space') then you would want more only if you plan on installing more stuff on the same drive, rather than using symlinks, right? or for storage, on the same drive, though only active programs need SSD speed, or first HDD partition speed; with the size of games these days, you might want 10GB to 50GB on your primary partition, imo