Weld around the top of the strut towers,down to where they meet the chasis rail & where the rails meet the fire wall remove the steering box & idler arm & weld in gusets you will have to drill holes for the idler & steering box bolt on & underneith where the chasis runs along the floor weld those too
The best thing to do is have a look at a few good rally cars that will give you a better idea how to do it
Oh yeh 1 more thing dont put to much heat in your welds & stager your welds
Good Luck

I was going to simply double up the factory welds (ie: drop a weld in between each factory weld)

I'll start by asking the usual, "where are you". If you fill in your location this helps others help you.

Then it depends if you really want all that chassis stiffness, ie high performance, track work etc (a cage and a few strut braces may do the job).

But if you want it done, you can do it yourself. Weld about 20-30mm long, then leave about twice that or more space between the next weld (to allow for chassis flex, otherwise it'll crack).

Make sure not to weld forward of the front strut towers or rear of the rear strut towers.

If welding thin sheet metal is not your idea of fun, there's plenty of places that should be able to help. I can give you a few places in Melbourne that do good work.

hi guys .has anyone done seem welding on their car.where are the best places to do it?
any help would be great.