My theory is that stuff like this converges on the most economic and market-accepted form factor over time. Look at airliners over the last half of the 20th cen

My theory is that stuff like this converges on the most economic and market-accepted form factor over time. Look at airliners over the last half of the 20th century - you had all kinds of weird and interesting designs (727, CV990, L-1011, Concorde). Now you invariably have a tube with two engines hung off the wings. Yawn.