I wouldn't count on it:I have this speakers from Magnat, THX Cinema ceries, they say they are optimised with klippel for horizontal and vertical disspertion. Interesting to see some real measurments but I think you dont have them in US. Probably some Arendals will show if there is really a design flow in MTM horizontal placement.
At 15 deg vertical there is already a droop ap at just below 2 kHz. Funny stuff happens below that as well. They should have done 30 and 60 deg, but probably then they'd have to explain some things... Obviously, the small tweeter makes it so that the effect can be pushed down a bit, but it's still quite noticeable.