The UV nail curing device might be using a more broadband and/or short-wave light source than the 405nm LEDs of the Form Cure unit, which could potentially give you different kinds of results. Depending on your goals with the parts, you might trying to cure them intervals of even less than 5 minutes before flipping them.
Are you hoping to compare the tensile properties you can get in these bars with our data sheets (hopefully pretty close!), or evaluating your printing and cure process, or what, if I can ask?