Cut rivet clearance holes on rudder bottom gusset

After confirming with TAF the suitability of this mod, small slots were cut in the rudder bottom gusset to resolve an interference between it and a rivet attaching the skin to rib 1. This notch extended 6mm across the surface of the gusset, to provide sufficient clearance for a 3x8mm rivet which has been shortened to 5mm. This latter length is sufficient to fasten together the 0.4mm skin and the 0.64mm rib1, with 1mm margin (inferred from Gesipa specs, which state a grip range of 0.5-5mm for the full 8mm rivet, thus 0.5-2mm for a rivet shortened to 5mm)