Looks good! If you have room to get to backside I dont see why you shouldnt be able to metal finish that patch without filler.
Get yourself a slapper instead of body hammers. They have a much bigger contact area, moves that metal faster and easier. Ive got a set bought from Ron Covell
www.covell.biz I use mainly the 3lb slapper, I use this probably 99% of the time doing ANY type of dent repair.
If you hammer and dolly after tack weld you will help control the metal wrapage. Just remember metal gets shrunk when you weld it. So you need to strench back out and you do this via hammer and dolly work.
To help find any low/high spots get yourself a magnum shrapie marker. The tip is about 1/2 wide, cost is about 4 bucks. You use the marker like a guide coat for primer. Mark over the metal, then take a good solid level sanding block loaded with 80 grit. The lows will remain black from the sharpie marker, the highs will be shiney metal. makes finding low/highs really easy. Also when you go back to raise those lows you can see the metal move up in those lows spots as the slapper/hammer smears away that marker.
Something else that came to mind. When you connect your welds together Ive found that you get better peneration into the existing tack weld and base metal if you grind down the tack weld before you weld into it. You remove any protruding metal that will be ground down later, then make your new weld into that old weld you ground down. No point in welding into a weld that will get ground down. This also makes your tacks faster as you dont have as much material to melt into here for you have less heat introduced into the panel...Eric