Be sure you have your HBP HPC signs ready to show the volunteers when you depart the runway, regardless of which runway you land. "P" if you are just parking, "C" if you are camping. Anywhere you park your airplane can be judged. They will give you a prop card at registration. Put that on your prop as, after judging, they will put a sticker on it (? green dot?) to show you have been judged.
If your information is in the window, that is a pretty small space and may not be large enough for everything you want to tell people. People might not go over to the window to read it. Tripods, unless you are sitting with your airplane, tend to go whatever direction the Wind is blowing. A sandwich board is a better choice. Many pilots will have the information on a flat board lying on the ground in front of the airplane. You can secure that (as well as a sandwich board) with tent stakes. The 'plastic cardboard' seems to be the best material. Good luck with the judging!!