I fit my tombstones with PVC (all spaced the same). I then have 16" rebar bars. I cut a jig which is nothing more than just a big block of wood with 2 pieces of rebar (same spacing as my props/tombstones) at my set height. I just place the block where I want the prop/tombstone. Insert 2 rebars pieces and pound them down flush to the top of the block. Pull the block up and off, and slide the prop/tombstone on. Plus since they are all spaced the same, I can quickly change tombstones around. 
You're welcome to stop by Big Nick and I can show you how I have it setup.
You're welcome to stop by Big Nick and I can show you how I have it setup.