You can absolutely increase the resistance for Gorilla Bow. The bands that are included with the bow range from 10 to 50 lb., but heavy bands, ranging from 60 to 100 lb. are also available. Gorilla Bow and Gorilla Bow Travel are designed to hold up to 4 bands, and up to 340 pounds in tension.
As a reminder, sneakers must be worn at all times when using Gorilla Bow.