I'm spending a lot of unnecessary time on this film where I just used a single colorbar frame + beep in order to keep track of my syncing when I received exports back from my sound mixer and colorist. My sound engineer told me that in protools it turned out to be 2 frames instead of the one I used in FCP, and now I do most of the syncing manually because I don't want to mess up.
My colorist told me there's a standard clip used by many professional editors which contains 1 'beep' frame and 49 black ones to generate 2 seconds (yah 25fps) of guidance before the actual movie starts, to help with the postproduction syncing processes.
Not sure what's happening to you, and what issues you are having.
I make a COLOR SOLID matte effect, make it white, drop it at the 59:58:00 mark for 1 frame. And then one frame of TONE from the BARS AND TONE effect...also at 59:58:00 mark. And sometimes I add one at the end. So when I get audio back from my mixer, I go to where they have the 2-pop tone, and mark that as IN, and in the timeline, mark in a 59:58:00...and cut in the audio. Pretty much in sync right away.
My understanding is that your audio pop is earlier...but it should still be the same. First time you hear the tone, that's the frame you need to mark in...and bam, should line up.