I have a small pond (1/3 acre). A friend of mine put 4 Smallmouth and 8 Largemouth bass in my pond last April. The size ranged from 14 to 22 inches. All have survived and seem to be doing well. One of the Smallmouth has already spawned and a couple of the Largemouth are nesting now. I don't know if there is any harm to stocking both of them or not, but I haven't seen any problems.
If the Smallmouth fry survive and grow well in my pond I intend to catch out all of the Largemouth if I can. I much prefer the Smallmouth to Largemouth. The Smallmouth puts up a much better fight than the Largemouth.

Larry