RFUMS M1 here - they also do Mondays and Wednesdays, but they don't always do 3 days a week, so you'll have to wait and see what they have when there are more dates released.
And FYI, that waitlist for dates can be pretty panic inducing. When you sign up for it, you'll get a message that you have to schedule your interview in the next available block of dates or forfeit your invite. So once you do, just make sure to check back on the scheduling site several times a day, as all dates fill up about as fast as they come out. They release new dates pretty frequently as the current ones fill up and they send IIs to more people, so just keep your eyes peeled for more options.
I know 3 days notice can be next to impossible to make for many folks, especially if you're coming from out of state and have to make travel arrangements, but anything else that might cause a conflict, be willing to reschedule/skip it for an interview. Priorities, ya' know.
Anything else I can answer about RFU, let me know