Workflow Help: 9:16 Footage Clipping in 1440x1080 Comp

Soon-to-be Studio user here (Speed Editor arrives tomorrow!), but for now I’m using the free version of Resolve and working through a project that reflects the typical workflow I plan to use for most of my content.

My goal is to output at 1440x1080. The footage I’m working with was shot vertically (9:16) in front of a blue screen, and I’m compositing characters into scenes using still images that are either 4:3 or 16:9 — none of them match my target resolution, which is intentional so I can add some motion (like slow zooms or pans).

Up to now, I’ve been using a workaround: copying and pasting a 1440x1080 transparent background node, then merging everything over that to lock in the resolution. It’s worked okay for a few clips, but it feels like there must be a cleaner way to establish and preserve a 1440x1080 canvas without duplicating background nodes for every composite.

The issue I’ve now hit is this:
I'm trying to composite two characters into a single shot. I trimmed the takes I needed and turned them into a Fusion composition, but now these two clips are getting clipped top and bottom edges on the keyed footage when I go into Fusion.

I suspect it's something to do with bounding boxes or scaling behavior in the Merge node, but I can’t seem to lock the canvas and framing the way I expect.

Any advice for setting up a clean, repeatable Fusion workflow that:

Forces or locks a 1440x1080 output canvas

Handles mixed-resolution source footage (vertical video, landscape stills)

Prevents alpha clipping or bounding box issues when merging multiple keyed characters?

Would love to get this pipeline dialed in before I move forward with batching out more scenes. Thanks in advance!

The Fusion page works at the native resolution of source media from the Media pool.
So if your source media is 1080x1920 (9:16) when you create a Fusion Composition using that media from a timeline, it will use that as its composition resolution.
If your timeline is set up as 1440x1080 and you want to force Fusion to work at that resolution, your best workflow would be create a Fusion Clip instead.
Do this by right-clicking on the clip on the timeline and from the menu choose New Fusion Clip near the top.
Fusion Clips = Timeline Resolution
Fusion Comps = Source Media Resolution

I'm thinking of:
1) instead of going with a single clip, go with two where the bottom one is a black at the resolution you want
2) in fusion if you comp the clip you have into a generated backside, you should be able to set the background at the resolution you want (but I might be mistaken here)

Hey

Since you seem to start from a Resolve TL (as opposed I'm very often on Fusion Studio form scratch for the record), you'd better set the final TL resolution in your Resolve settings, then superimpose your clips there > select them and > right click : new fusion clip ...
It's the reckoned way of locking the resolution and the link between pages...

Now, be aware that your transparent BG trick is still very used and efficient, you may want to make a Fusion reference comp (that I don't use either but which is also designed for re-using templates as you may need).
But you don't need to copy/paste anyway, creating it takes 4 s. and you could even make a temporary default setting of this resolution for the purpose of your project
Also, you may want to play with a Letterbox node which allows you anything in case of...

Thank you all for the helpful replies to my earlier post. I’m slowly but surely getting more comfortable with Fusion. I’ve managed to lock in my desired resolution by starting the node flow with a Background node set to that resolution and carefully merging everything on top of it. Also, using the Speed Editor to roll through frames has made keyframing animations much easier.