This is from Jan 31 rawhide. I went into disk druid during a laptop install. This laptop has a 20G drive, geometry is reported at 2432/255/63 by disk druid. After wiping all partitions I add a partition of / with size of 1M and grow to fill disk, it only actually allocates 8032M and reports the drive as being 42% full at the bottom. I tell it to add a /usr with the same size and to grow and it allocates 9546M for that partition and marks the drive as 92% full at the bottom. I remove hda1 (slash) and hda5 (/usr) is no 19077M, showing it taking up 100% of the hd at the bottom.
Make a /boot partition. It is limiting the size of the / partition because it is the partition currently containing the kernel, which cannot go above the 1024 cylinder limit due to BIOS limitations. The newer version of the installer which be more verbose about this.
Can it be made to not worry about that if you have supporta for lba32?