How to customize fzf backend and frontend?

[Gorthog]

I would like to use bat for file preview and use fd for file search.

I tried the following for fd:

set FZF_FIND_FILE_COMMAND 'fd --color=always --hidden --exclude .git --type f . $dir'
set FZF_DEFAULT_OPTS --ansi

Seems it's being completely ignored? Hidden files are not shown and I do not get syntax highlighting.

Also for using bat i tried this:

set FZF_PREVIEW_FILE_CMD 'bat --color=always --style=numbers,grid --line-range :300'
set FZF_COMPLETE 3

Which is almost working - the only issue is that scrolling works only when mouse pointer is in the marked area. scrolling of the left area (files and folders, not preview) works as expected.

When I switch to full screen, file preview scrolling does not work at all, no matter where I place the mouse pointer.

Not sure if this is a bug, or just mis-configuration on my behalf.