Matt, When was the last comp 400 you did? I know you felt like you were ready for 54.0 a little while back, and then got dinged. Did you ever get one in? I recall a killer “fartlek” treadmill session you posted (something like 8.0 for 60sec/14.0 for 60 sec up 3% grade) for 3 miles, and thought that was extremely strong (as in my heart would burst even trying it) but should have made a 54 a breeze given your 12.0 100m.
I will run once more this year at least. Maybe twice. Will do a 200 for sure and a 100 or 400 (or all three).
I think 54.0 is definitely doable, though not a breeze.