The entire basis of this conversation can completely be summed up in 2 words..
TANK SIZE.
There is a thousand x + y = z variables, and we could sit here and discuss all the 'what if' possibilities, but unless you are working with 1000g+ plus size tanks, then there isn't much to debate.
If you do have a 1000g+ tank, then there is a good chance you have an idea of what combos could work based simply on experiences..
The bigger the tank, the more viable 'un-acceptable' options would be..
In general though.. Domestic Stingrays should be kept with; Domestic Stingrays. Tankmates, IMO, are for the advanced stingray keeper.