So I am about to begin my third year of undergrad physics at a private school with a relatively unknown physics department. Because I came into college with a lot of AP credit, I am able to graduate at the end of this year with BS degrees in both physics and math. I have an excellent GPA and am expecting a PGRE score in the 750-800 range, based on practice tests. My worry is that I won't have sufficient physics research experience heading into grad school. I just finished an REU in theory/computation, and will continue to work on my REU project upon returning to my college. I am told that if I get results on my project, there is a reasonable chance that I can get them published. Unfortunately, this is my only research experience. As a NCAA student-athlete, it is pretty much impossible for me to do research during the school year, since my sport+classes+homework take up so much time. I want to get into a top 20-30 physics grad school. Should I delay graduation and stay in undergrad for a fourth year in order to gain further research experience? Or will one REU with a possible publication be enough for the admissions committees at these competitive grad schools? Appreciate any advice.