And using LVM for "partitioning" bypasses a lot of this silliness. Do 'lvcreate --contiguous' and you should be good to go if you're using most any non-toy initrd.

Given that every r/w filesystem you're going to use as your '/' on a Linux desktop or server supports online growing (and most support offline shrinking), it's nuts to me to hear people worrying about getting partition sizes correct. With LVM, if you get it wrong you just resize the LV and the filesystem it contains.

Hell, LVM makes swapping out disks a really easy online operation. [0] If you don't have nice hot-swap drive caddies, you might have to power off the box once to add in the new disks and again to remove the old ones, but all the data transfer can happen while the system is in use.

[0] Assuming the new and old disks have the same logical sector size, which they usually do.