Minor travails and new access panels to very tight spaces: When drilling a hole through the side channel upright on my fuselage, down by the landing gear fitment where the holes go to attach the seat pan, I noticed that the drill seemed to not want to go through the sheet-metal -- about like when metal is a bit thicker. So I used a little bit more force. But it turned out it wasn't sheet-metal. On inspection I saw that I had drilled into the nut of the top AN 4 bolt of the rear part of the starboard fitment that connects the front fuselage to the rear fuselage. I couldn't tell how deep I had drilled into the nut or maybe even the bolt. I was unwilling to ignore potential damage to part of the system that connects the rear fuselage to the front (everything might NOT be all right). So began an hours long endeavor to remove the bolt and nut to inspect and replace. It involved getting a 20 ton press, buying a wrench or other tool that I could bend in the press to a U-shape to be able to get back behind the side channel via the narrow area left between baggage floor and seat pan rear support. I knew that I could put an access panel instead and approach it that way. But I started with the "make your own tool way". I managed to remove the nut from the bolt, but had so much trouble getting a new one back on with a washer. Then my custom wrench head got stuck. I was forced to make an access panel. Once the access panel was open it took a whole 2 minutes to remove the stuck tool and reinstall the bolt and torque it correctly.