Rendering same project at different frame rates

I have a number of projects where I need to deliver exactly the same output at different frame rates (25fps and 50fps). The frame rates should be the only difference and the perceived speed of the footage should look the same.
I have edited the original 50fps footage in a 50fps timeline and successfully rendered the 50fps version. However, when I wanted to change the export frame rate to 25fps under "Render settings" on the Deliver page 50fps was the only option available in the dropdown box. Next I tried to change the timeline fps to 25, but that option was grayed out. I could only change the playback frame rate, but then all footage was simmply speeded up.
What would be the best / most effective / easiest method to render a 25fps version of a 50fps project?
(I am using Da Vinci Resolve Studio 17 Beta 6)
Thanks!

Create a new timeline at 25 fps and Copy/Paste the footage into that.

Thank you! I really appreciate your assistance.