I have a microrouter though not the V4 and would have no issue cutting a slot in the base of the cabinet (there is already a hole in mine for a vacuum table) though to be on the safe side I would keep it as small as possible. The cabinet is fairly substantial and the base is 2 or 3mm thick at a guess. My cabinet base is a single layer but is stiffened with the sides and additional U sections welded on but they aren't in the centre.
Before buying make sure that it is either complete with the Denford software or has been retro-fitted to run on something else otherwise the cost of an upgrade and/or software could be a deal breaker.