Need help ASAP since I'm working on the cake right now and it's due this evening.  This is my first time using modeling chocolate where I need it to be really firm.  Other times I've used it as a covering over my cakes so it just needed to be the consistency of fondant.  I made the Craftsy recipe that uses 2 lbs candy melts and 1 cup corn syrup.  It sounded like a lot of corn syrup but I used it anyway.  The modeling is the consistency of fondant and won't get hard.  I'm making panels for a box so I need them to be firm so they will stand up.  I cut the panels out and put them in the refrigerator, but once they returned to room temperature, they got soft again. 

I'm afraid I'm going to have to scrape the modeling chocolate idea and use fondant mixed with tylose or gumpaste.  Does anyone have any suggestions how to make the modeling chocolate firmer so I don't have to start over? PLEASE HELP!