Is there a command I’ve missed or a series of commands that’ll let me stick one surface onto another…sorta like sticking a Nixon sticker onto your bumper? 
Hello - In this case probably the best is to split out a piece of the larger surface (copy) that has the outline of the smaller one. DupBorder the smaller curve and in a view looking straight on at the larger one, Split the larger one.But… what do you really want to do? Put a second material on there or?
-Pascal
Using this model as an example, I’d like to explore different window shapes and sizes WITHOUT actually going through the process of cutting out the cabin sides like I’ve done here for the larger windows. If there were a way to just stick a window shaped surface onto the cabin side, it could save lots of time.
Hi,
draw the outline of the window in 2d on cplane.
Project to the suface you want in side view.
Built a surface fom the projected outline.
Move that surface some mm in N direction with gumball
Or copy the surface you want to put the window on in place, move some mm in N direction, project the outline curve onto this surface and trim with that curve. Extrude srf if you want.