Small, immature, summer squash (or zucchini) work best for dehydrating. Pick them before seeds form inside. Wash and cut into 1/8-inch slices without peeling for "chips" and 1/4-inch slices for rehydrating. I use a mandoline for cutting the slices so they are the same thickness. If you place similar-sized slices on the tray, they will dry in approximately the same length of time. So I put all the smaller end slices on one tray, until I have about 3-sizes of slices on three different trays.
Dry thin slices for chips until dry and crispy in a 120°F dehydrator. Thicker slices, dry until leathery to crisp.
It's also important to dip the slices in an acid bath before you dehydrate them, or blanch for 4 minutes in an acid water solution, drain and dehydrate. This will aid in preventing bacteria, including Escherichia coli O157:H7, Salmonella species and Listeria monocytogenes. Use 1/4 t. citric acid to 1-quart water.
We use thin-sliced dehydrated summer squash and zucchini as a replacement for potato chips at our house.