Hola Gringo ....
Not that much farther to go around the mountains ... guard against the traps that look like valleys ... "scouting" .. is worth it every time ... of course then you only have to remember all you learned
They'll draw you in thinking it's a way around ... only to find it's a dead end.
The only trade off is time and that deserves a good look because it could well be the same if you figure the slower speeds you net going straight up and over ... not to mention fuel burn is ridiculous ... don't remember seeing a distance category ... if it equates to time savings fine, but don't be deceived and not only wind up with no real time savings, but a kick in the butt on fuel burn ... or worse!
Each one's different, but your scenario seems to show up mostly on flights that will allow a lower cruise altitude for the majority of the flight ... then the ever tempting climb over ... not always the best economy.
Also have to figure on diminished performance at higher altitudes ... greatly amplified in the vintage aircraft ... thinner air makes it easier to "cut" through, but with a normally aspirated piston engine, it's also harder to breath ... the power just isn't there.
We're going to have fun just taking off from some of the airports further south for the same reason.
Tonnage is going to be a bit on the weak side compared to the larger aircraft even if you hit every delivery stop ... and the DC-3 ... as you eluded to earlier ... sure won't set any speed records ... No need, just be mindful of the 27 hour total ... generous if my early numbers were even close.
A clean Maintenance record, tight eye on fuel, total number of airports are the only areas in this event that you can consider in a DC-3.
More fun than a barrel of monkeys!
Recorriendo la montañas!!
Happy Trails Amigo ... 
