Hi Manisk,
the guitar is looking great.

"I like it but id really love getting a fade from very light around the tailpiece and darker along the edges until it meets the mahogany back, and make it so you cant really see the gluejoint that well, i have a jar of mahogny colored stain and also a graphite-black one - how do you recommend i approach it? - or would you do it different? I really am making it up as i go so im interested in your opinion"

I did a stained black to jarrah burst on my FBM-1 and the TB-4 builds using FW stains. Both reasonably successful. I did the jarrah all over first, let it dry, then added the black and using a clean rag tried to blend it in. I had to do the black a couple of times and the blending took quite a while.

Looking on Youtube most videos blend the stained burst while both colours are still wet. I found this quite challenging on scrap wood.

I did a few experiments first. On scrap wood I also tried doing the black first, trying to feather the colour. Then sanded back to get a good transition. then added the jarrah.

I don't think there is any perfect way to do it. I settled on the first method as I thought it was easiest. Worst comes to worst it can always be sanded back if you are not happy with it.