Hey @Bengy, are you referencing the Floodlight Wired or the Floodlight Battery for the Smart Lighting devices? For the Floodlight Battery, you will need to install the bracket that the device slides into, so if you have somewhere where the previous light was installed to screw in the bracket, you should be good to install it up there! For the Floodlight Wired, there is a junction box that is needed for the install, which you would need there to be a junction box where the previous lights were.
Other than that, feel free to get creative! The Floodlight Battery has more flexibility with where it can be mounted, so if you find an area where you can makeshift the bracket to stick to or be screwed into, and the Floodlight stays in place, then you should be good to go. Hope this helps! 