Almost an hour spent grinding the fillet down to fit neatly into the gap. It's not perfect, but near enough to fit. Started welding it into place, getting the welds underneath it proving to be difficult again, although the welds above are turning out fairly neat. Changed to an Argon/CO2 mix because my CO2 cylinder ran out. It's different from the pure CO2, less splattering, but seems to require a higher wire feed to stop the weld bead from clawing it's way back up the wire.
Still paranoid about my welds, and ground the accessible ones around the fillet back to check that they had penetrated properly. Will run another uick bead over them tomorrow. Jacked the front end up higher in order to improve access underneath for welding. Will take the front sub-frame off again at some point in order to get the last few welds that are on the inside or underneath done.
Cleaned up the remaining edges of the new drivers side wing. The Fein multi-tool really makes it a doddle. Still have to add the additional fibreglass support to the rear of the wheelarch, and still have to clean up the headlamp hole.
Started re-assembling the drivers side suspension assembly, but realised that I can't find the large nylocks that hold the stub axle onto the balljoints on the upper and lower suspension arms. Was able to take one off of the damaged suspension components but the second one had jammed in place. I'll have to properly clear out the garage to find them, but I've had enough for today.