oooooh that's great i been trying to do this myself with quiet poor results. But using the info you gave above i managed to make 2 planets one at about 0.7au and one at 1.2-1.3au (I'm guessing here, i don't know where to find info on this?) They both stable, and haven't got enough pull on each other to wreck each others orbits (not yet at least).
It was interesting though, i started the simulation with your settings (+ double the mass and slight larger sizes) and after a few hours, i relabeled the objects that had got much bigger as possible planets. I labeled them in order outwards, so i had PLANET1, PLANET2 up to 4 large objects.
In the morning after 110'000years, only PLANET1 had survived, as well as a newer object that i had not labeled as a possible planet back in the days. PLANET1 hand migrated outwards slightly and the "New" PLANET2 was probably one of the lowest points of the original belt system that was in place. I kept PLANET2 as its original name even though its now the 1st planet.
Sol = 2x sun mass, 1.8x dia
PLANET2 = 2.08 earth mass, 1.262 dia
PLANET1 = 4.32 earth mass, 1.6 dia
I'm now trying to build up an outer plant the size of Jupiter, but that means adding a lot more objects and mass, which in turn slows the Sim right down. I think i doubled my mass and dia of objects in this outer ring, and i added "only" 300 objects (it should really be double or more, 400+ really?)
This belt has already grown 3 larger objects, which again I've labeled and colored differently to the belt system (which is white).
Will post pictures soon of the progress