you're right, I'm only in my final year of secondary school with little flying time in a C152 and a Harvard so I've based the design primarily on what I've seen in the past.
I understand that tri-jets were only developed for reasons of power plants being under-powered at the time as you have said. Instead I might put more focus on my EC-20 design with the possibility of an APTU which if I remember correctly was considered in the Boeing 777 design during its preliminary design phase.
As for the L-1011, that is still perhaps my favorite airliner after the DH-106 Comet.