Dan, I will not be able to bring a game this year due to work obligations, but I have two suggestions.
1) Post some type of sign outside down by the loading dock ramp letting people know “This way up”. I must have driven around the block five times until I found the ramp entrance.
2) Forewarn people that they will be setting up the machines on concrete. Maybe a friendly reminder to bring something to set their glass on when they remove it.
Here’s mine from last year.