Clean up old tape and flox ooze from earlier processes
The frame / plexi joint will receive a body filler bevel to smooth the gap. From there, it will receive paint just beyond the filler to form a clean, crisp edge.
I set the filler bevel to an inch (the width of my tape and then taped there. I applied filler to the void, smoothed and sanded it until the surface was consistent. This took at least 3 filler applications. I can tell this is going to be very time consuming.