I'm planning my run and am almost ready to start digging holes for the 4X4 support posts. Does everyone use concrete to strengthen their runs? Would gravel work ok packed around the posts? I like the idea of knowing the posts aren't going anywhere in concrete, but I also like the idea of being able to dig up the posts if we decide to change the run at some point. Also, what do you use to stake down the apron outside the run? I have some 2x4 green garden fencing in 24" length someone gave me which I want to use for my apron, how is the best way to stake it down?