Place the moonshl2 folder in root of your TF card.
Now look in your moonshl folder for a file named moonshell.nds.
Move that file from \moonshl to the root of the TF card.
Next copy the file named moonshl2.nds into the the moonshl folder.
Last, rename moonshl2.nds to moonshell.nds.
EDIT
I forgot an important step. To allow resetting from moonshell 2 back to EDGE OS, do the following:
Copy \moonshl\plugin\reset.mse to moonshl2\resetmse\reset.mse, and then rename it to EDGE.nds
End of EDIT
Now, the middle button will run moonshell 2 and running moonshell.nds (in game mode) in root will run moonshell 1.71.
Most of my older DPG video files will run using moonshell 1.71, but not with moonshell 2.05.
So I keep both MS 1.71 and MS 2.05.