I've been using 4i speakers for Tops for the last few years now. They work, but I must say that I only used them because I already had them. The 4i speakers are what I used when I went from 3.1 to 5.1, then to 7.1. Then I got better speakers for Surrounds and moved the 4i speakers to the ceiling for 7.1.4. The 4i speakers were chosen for cost when I originally purchased them, and they needed a lot of help from subwoofers to work pretty well, and I've been happy with them for the most part, even though they needed a very high crossover to the subs.
Last week I installed the first pair of replacement speakers for the Front Tops, and this week I'll install the second replacement pair. They are not ML speakers. Partial disclosure, I knew I wanted these new speakers for a long time because I've heard them in another installation, and I needed ceiling mounted speakers. They are made for outdoor usage and come with really nice brackets, and they ACTUALLY measure down to 49Hz, which is about 70Hz better than the 4i actually measured so it's a great improvement.
I'm saying all this for background info, and to say that you should get very competent speakers when possible. For me, this was possible a month ago.
Also, when I installed the 4i speakers I used 45º as the angle shown in Dolby ATMOS diagrams from MLP to the plane of the Front and Rear Tops. Now I'm using 50º and it seems to work a lot better for overhead sounds. This is measured from MLP to a line drawn between the front or rear pair of Top speakers, not from MLP directly to EACH speaker which will lower the angle.