Unfortunately work kept me from much building this week...bugger! But the way that the spar caps are shaped means that it is impossible to get my counter sink tool up close to counter sink the holes on the spar cap as well as get the rivet gun up close as well. The home made holder works a treat in drilling the counter sinks, I used a roll pin through the hole of the bit to hold in place and the other bit uses the AN426 driver above the AN470 driver with an aluminium plug between the two to hopefully prevent any damage. I haven't tried it yet! I've got another couple of hours or so of up drilling to the final size and deburring and then I will find out if I get my clever dick certificate.