Gimp keeps cropping my perspective rotations

I'll admit that I'm kind of gimp newbie. I want to crop an image, do some perspective transformations and then have the resulting image not cropped.

But gimp keeps cropping it. I've figured out a workaround though: just promote what is called a "floating selection" to a new layer.

Here's my original pic:



I crop it:



Now I do a Tools/Transform Tools/Perspective:



And after I get it to correct the perspective into straight lines:



And then I click on transform:



But you see that the floating selection is outside the original rectangle of the crop. So we right click and Image/Fit canvas to image:





and now the canvas has expanded:



but we're still not done. We need to promote the floating selection to a layer. Right click on the floating selection and choose To New Layer:





Now you want to right click and go to Image/Merge Visible Layers and choose expanded as necessary:





And now it's all back to a single image.

Before merging visible layers:



After merging visible layers: