I'm thinking the micra k11 will be similar to the Nissan Figaro I recently restored (1991) I think you'll be in for some fun...the Figaro is mostly less than 1mm steel...I think 0.6-0.7mm if I remember correctly. I've not used flux cored wire...but I've got a descent gas mig and it was still a bit of a struggle. What you need is a mig that can weld low amps....dunno how good gasses will be? Most of the body welding will be using the stop/start approach...basically a series of tack welds put down with a small pause between each tack...having a copper plate will help too behind the weld but that won't always be possible. Doing welding runs on thin steel will just blow holes. The up side is I think if you can get the hang of welding a k11 I reckon you'll be set to weld most things!