You're exactly right. Here's a chart that you find handy:
Partition Size Cluster size
Less then 512MB 512 Bytes
< = 8GB 4 Kilobytes
< = 16GB 8 Kilobytes
< = 32GB 16 Kilobytes
> 32GB 32 Kilobytes
Honestly, as long as you keep the partition size less than 32MB, you won't notice a whole lot of wasted space difference. Heck, you've got an 80GB hard drive for crying out loud!
Just as a sidenote: the inner portion of the hard disk is "slower" not faster than the outer. That's why it is always best to keep the system partition at the beginning of the HD.
~cdogg