You should bake directly in the disposable pans, without setting them into another pan.
Nesting them into another pie pan could actually create a small air barrier between some parts of the disposable pan and the nesting pan, and therefore create an insulating effect. If the second pan is much darker, and therefore absorbs radiant heat more effectively, you may get splotching or uneven crust development (disposable pans tend to be very shiny, and so reflect infrared heat well).
You may set your pies on top of a sheet tray, if you are worried about overflow making a mess in the oven, or to make it easier to move them in or out of the oven. This also tends to slow bottom crust development.
If you are worried about under-developed bottom crust, pre-heat sheet pan in the oven, and place the pies directly onto it. This will give a head start to bottom crust development.
At the extreme, you could use a pizza or bread stone, but this is quite likely to go too far.