I've made the board to be the size of the humbucker, that came with this guitar, so I knew it would fit. But I still didn't figure out how I mount it on the pickguard yet. It's not that important on this stage. I've taped the PCB directly to the guitar body, connected the headphone amp and made some sounds. I placed small magnets on sides of the relays, they're just holding there by their own magnetic force.

I'll post a video if I figure out how to upload it here :D