Nice joddler and good job on the repairs. When you come to do the other side Martins panel should already be joddled (unless you are cutting it back). I usually hold the panel in place with tech screws or skin pins (if you use tech screws or self tapers drill the top hole slightly big and just nip the screws to allow for a little movement) then, as you've done with the repairs you've already done, tack every inch or so working first from the middle then each end in turn letting things cool every now and then to prevent warping. I wouldn't attempt full runs as it puts too much heat into the repair, just keep tacking until it's good and strong. The tacks you've already done look plenty strong enough and won't leave a lot of material to grind off which can also generate heat and warp the repair if you go too mad with the grinder. I've also found that flapper discs tend to take material from around the weld and thin it off so I've taken to using a proper disc, which you can have more control of, then finish it off with a coarse sanding disc.
Hopefully I'll follow my own advice as I'll be doing the same job soon along with the inner and outer steps on Harvey.
Good luck