OK, so far so good, I have been sanding on a flat(ish) surface … not dead flat, but enough and with the innards all mounted up (listened to Paul’s video!). I guess what’s left to do is simply ‘more’ of 50 grit sand paper to reduce the hump. This may well be explained by the welding (or the drop forcing the need for welding). This will bring the full sole to a even flatter state.
This isn’t a tool to send men to Mars so ‘good enough’ will apply.