I don't have any data on this, but I've found that when my teasers cover, most of the time I didn't even need the points, should have just placed single bets. and I have lost MANY teasers where one team coverd and one didn't, would have split had I placed individual bets.
The teasers I have the best luck with are usually teasing an underdog and an over/under. For example, last night's Pitt/Jax game I was going to tease Jax to +9 and the over down to 29, would have won. I ended up just taking Jax +3 which covered anyway.
I'm sure there are others in the forum with more/better advice than I have to give. Bottom line: I don't play many teasers, and if I do it is not for much. GL