Doing an observership in the US during F1?

Im currently a 4th year med student and I'm thinking of continuing training in the US after I do the 2 foundation years. I have already gotten the ECFMG number and I'm thinking of sitting USMLE step 1 during 5th year. Money is quite tight right now, so doing an observership in the US at the moment is out of the question. I am thinking of doing the observership sometime during F1 or F2, but I dont know if that is possible as most observerships are 4 weeks long and I read that F1 doctors only get 9 days per 4 month rotation off.

Does anyone know how I may make this work?