So ... I had a pretty similar situation, but not at as high ranked school (Tulane). 240s Step 1, waiting on Step 2, top 1/3 of class (many honors pre-clinical, HPs and Hs in clinicals), good letters and extra currics, but 0 research.
I thought about what you want to do - 1 year of research, but decided to roll the dice. I applied broadly, and interviewed/ranked at 7 places, and thought I made a good impression. I ended up not matching ... it's still a bit heartbreaking, but looking back, I am almost positive I would have matched with some research, especially if I took a year off. So, I'm going to get some research done before internship, hopefully do a little during the year, and give it another go ...
So, all in all, I think we have similar stories, but you're going at it a different way. I think with a year of research and some good letters from UMich faculty, you are going to be an excellent applicant.
... next part doesn't totally relate, but it's been in my head ...
After doing the interview tour, I picked up on a few things. The same people were going to the same places. The hotshot applicants were going to all top programs, i.e. at the UCLA interview, everyone was from top 10 med schools, and 3 had just gone to the Harvard interview the night before, and everyone knew each other. I knew no one ... a little overwhelming!
The rest of us go to our regional mid-tier programs (i don't believe in a low tier for rad-onc), and we see each other at pretty much all of them (in my case: Ford, Wayne, Loyola, etc.). There is some overlap - that's why I was at UCLA, and that's why superstar hotshot girl was at the Wayne interview. But not too much "mixing"
So, I feel in terms of applicants, there are three groups, and I realize this is solely based on observation. I'll start with this - almost every student in all three groups are top 1/3 or higher in their class, and have 230+ on step 1. What that means is if they are normal, nice human beings that can hold a conversation, they can match in almost any field (save for Derm and Plastics), and I find that impressive. There's some outliers in terms of stats, but they may have PhDs or good # of pubs, but I'll leave them out for simplicity's sake. So, here is the groups ...
1) Surely match 2) Decent chance of match 3) Most likely won't match. The #1 group matches, if they go on their 15+ interviews and rank them all. The 2nd group will get 10-14 interviews, and if they rank all programs, there's a really good chance of matching. The 3rd group gets 0 to 9 interviews, and is playing roulette, but still can match if they interview well and make a good connection.
Now, to tie it back together, to move from group 3 to group 2 is the critical transition to make. And that's where research comes in. That's where you get the critical mass of interviews, if you have a baseline amount of research (radonc, medonc, radbio, biophys, then everything else). Also, this is where LORs come in, especially famous names. There's a thread with these names - make sure you have at least one of those. Going from 2 to 1 is even harder, and it takes AOA status, ridonkulous step scores, MSTP from a top school, etc. Basically, everything everyone else has, plus something that just sets you apart.
With almost every program on ERAS, if you really want to be a rad-onc, there is no reason to not apply to every program (you've already spent $100,000-$200,000 for med school, what's another $10k?), unless you are group 1. Then, when you overshoot and get 20+ interviews, you can be somewhat selective. If not, go to all of them, and rank them all.
Anyway, that's my theory ... I'm sure people may disagree, but I think the field has gotten so difficult to get into, that you need certain threshold items on your application to have some certainty. And research is definitely one of them.
Simul
