Here is my outdoor setup.

I was using almost the same setup successfully on two different tracks with a LRP X22 13.5t Motor, set to 40° Timing, 5.0 (100/37) gear ratio to match similar Top Speed as the ETS Combo and a LRP 6700 Graphene 4 Battery.
I don’t recommend this setting if its an open 13.5t category, but wanted to have a „medium“ speed to test with.

Changes suggested from this setup for Stock:
- Rear spring 2.6
- check your weight bias if possible to keep it around 50:50 front to rear (different electronics/batteries/fans will have an influence)
- Less toe-In if it does understeer too much (didnt needed it as it kept corner speed)

I can recommend to use RTC for stock classes on outdoor tracks especially if they face lower grip, however if you run the standard suspension, I would start with:
- 4.5mm hex width
- N/A 4in, A 3in
- Upper links, 1.5mm inside, 1mm outside
- Wheelbase 1.5mm front, 1mm rear
- Droop 2.4mm measured underneath centre "bridge"

As the RTC is heavier, I would consider shifting some weight forward to keep balance. Or do change to the forward battery position.