This design is based on the SLS Block 1A Cargo version, although it is slightly thinner(only has an 8m wide fairing and second stage) and a mere 61-ton payload capacity. ANd it actually works well. I've launched 2 dummy Lunar payloads and 1 dummy payload into GTO. Along with several test flights.
I'm currently aiming to make a 100-ton+ version of it.