Does any one have trouble with their dog (s) digging? We are going to get a pen for Sophia so she can be outside sometimes while we are at work (once she is big enough and it warms up outside in the spring). We have a very big yard but it is not fenced in....we are also located on a busy highway so I do not want to take the chance of her getting hit.....thus the pen. However, my fiance seems to think there is no reason to concrete the botttom of it .....I of course say otherwise <_< I want it concreted for two reasons: 1) to keep her from digging out and getting close to the busy road (how my last dog died )...and 2) so it will be easier to clean out when needed. Anyone have any experience with this????