Screw splice gypsum with sheet metal strips

[MagnusRö]

I have a slanted ceiling with horizontal battens 45x45, cc 300, which I am covering with vertical gypsum boards. I join the short sides on a batten so they are screwed according to best practices. On the long side joints, I use a metal strip that I bought at the lumberyard.

However, I don't think the joints are as stable as I expected with this metal strip. I screw with cc 150 and with screws in each batten (See picture). If I had used plywood as joint material, it might have been more stable, but perhaps that's overkill?

Am I doing it right?

 

[Beppo]

I fixed the seams with leftover råspont. Some plyfa or a piece of OSB would probably work even better as it's a bit thinner and easier to fit.