My suggestion if you currently have a shoulder issue, have a problem rounding the back at the bottom of the squat and want to run smolov.
Find a box set to a height that you can hit without starting to round the back. Use a friend or a video camera to find the correct depth that you can use.
Once you have set the correct height, you should try a 1RM, or if you don't want to do a 1RM either estimate what you think you can do to that depth, or just do some repetitions and use a 1RM calculator to estimate the 1RM.
Then for the actual smolov itself: Start off doing the base meso cycle, and then you will see after that if you want to continue, the base meso cycle alone will pack 5-20kg onto your squat alone. Usually for me, I get 10kg from this cycle.
If you use a high bar position, and position your hands with maximum width, close to the collarss, this will take away a lot of stress from the shoulders, and your shoulder issue should not be a problem.
I am using such a technique here:
Although you do not want to go as deep as I do in those sets (ie. the rounding problem of yours), you could use the same bar position and hand placement.
Lastly I suggest taking 10 to 20kg off your 1RM before embarking on the cycle. This will make the whole experience doable, and the risk of injury far less risky, and I promise you, you will still make gains. Don't add extra sets to any of the workouts, this could potentially mess up the recovery, and you might starting missing sets the next session.
To reduce the stress on your body even more, without sacrificing strength gains, you could do pause squats for the entire cycle. I did this, and it transfers perfectly to the ordinary squat. Poundages gained in the paused style transfers directly to the ordinary squat.