Hi CNCexplorer,
No matter what you do, there will always be something better and so everything has to be a compromise. However, I would suggest that you go for 'fully supported' rails on the X axis (if not both X and Z) - there is not that much difference in price.
Although wood is easy machining if you start V-Carving then 'chatter' or tool vibration can spoil the work so rigidity is an important consideration here and unsupported rails (less than about 25mm dia.) can flex a lot more than you would think.
Tweakie.