It's certainly possible. I graduated last year and knew a few people who did this. To make it work you basically have to minimize your step 1 study time to start clinicals as soon as possible, and then do all your rotations back to back with little or no breaks during those 90 weeks. When I did it we still had 12 weeks of 5th semester, which apparently has been decreased so maybe that gives you a little more wiggle room.
So you can definitely do it, just realize you will likely have little or no dedicated Step 1/2 study time (i.e. will be studying while in classes/rotations), and will likely have to line up all clinical rotations back-to-back. This will limit your ability to schedule specific rotations you might want to (i.e. non-affiliate rotations in your specialty of choice, etc), as well as having some much needed downtime during those years.
I actually started with the plan to try and do this, but abandoned it after 4th semester when I realized that attempting to squeeze everything in would likely hamper my ability to put forward the strongest residency application possible.