This is May of the end of your 3rd year/beginning of your 4th year, one calendar year before you graduate? Or the May at the start of 3rd year? Comments on both:
1. May of the end of your 3rd year/beginning of your 4th year. This was like my situation. My school starts 4th year early. VSAS didn't open until the beginning of April, and the earliest available rotation slots were in June. I did one in June. No problem for you to wait an extra month until June. If you've already done your home rotation and it's Feb, 7 months before you apply, you're ahead of the game.
2. May at the start of 3rd year. IMHO, this time point is too early to try and get connected to an away program. They will all but completely forget you by 16 months later when you finally apply for residency. If you'd like to get connected to another hospital in order to arrange a year off of research with them, that's one thing. Otherwise, I would advise you use this time to do research with your home program, rather than struggle to arrange an away that will yield low returns. If your school will let you schedule a research rotation for a month, great. If not, schedule a slack rotation and do research outside of your hospital/clinic duties. It can take quite a bit of time to get a paper through the publication process. Better to start as early as you can, and work towards strengthening your CV before submitting your app 19 months from now.
That help?