RB6 is just great indoor, fast enough, very reliable and quite safe especially on jumps. You got to work on it even if last setups available already include all work done in a year or so.
Flat arms with 3rd holes, shorty, a bit of weight and you're done.
On the other hand the DB1 (I got one too) is very fast but I have to keep everything in control more.
One thing that was very valuable indoor was to use a SP front end (larger front block with shorter wishbones). The car was more smooth on sweepers and large corners (like after a straight), a bit less flashy on tight chicane but overall safer.
I would try BB on the RB6 with AE kind of setup (2 to 3 holes), look at Tebo setup. I tried 3x1.3 with harder oil for the rear than with smallbores (35/30) and the car was fast yet safer on 5min without loosing too much.
You can win any race with that car yet easy to run and to service.
Now I wait for the DB2, Tony
I would look at Xray soon to be released 2wd. Not so good for low grip for sure but should be a rocket indoor without being too expensive (no options needed).