Although it may make sense for real estate inside your enclosure rearranging a pack that is currently operational rarely make sense for your wallet.
If you head over to the battery builders thread you can see what all is involved in making a pack and what you would have to do to tear the pack down and rearrange it.
Meepo sells their enclosure’s for ~$30usd and is the cheapest out of the box option I can think of to use in this scenario.