We're real new to RVing, in fact we don't actually get our RV until next week Anyway, we're going to be using it in a dry area that is not very level by a long shot. There are no jacks built in to this unit. What would be the best way to get this level? Front/back...side/side... What would be the best thing to use? We're talking about up to 12" here Any help would be appreciated! Thanks!