Next time you're going to tackle a particularly large or time-consuming embroidery project, consider using wooden stretcher bars as both a substitute for a hoop and an easy way to finish your project. Once you've completing your stitching, it's easy to stick a nail in the wall and pop your work right up!
I've purchased stretcher bars from Jerry's Art-A-Rama and AC Moore, but they're available at any any typical craft or art supply store. Price varies greatly with length, and you often receive a discount if you buy multiples of the same size.
The number one trick I've found when using stretcher bars, not just for embroidery but also for mounting fabric panels, is to use a rubber mallet to beat the bars together... and enlist someone stronger than you if you have stick arms like me! If you plan to use a hoop and then mount your work using stretcher bars, be careful to look at the work as your stretch it to make sure you don't distort the image. Also, don't forget to leave a good couple of inches and extra fabric around the design so that you have room to wrap the fabric around the bars!