A few setup questions

[dibble34]

Have spent a lot of time reading and found a lot of useful info, however some of it has confused me slightly

So i have 3 questions

1 - I run at a high grip astro track so used 15k & 7k oils as after reading up it looked like thicker oils would be the way to go. However the car was quite edgy and a friend who was running much thinner oils seemed to have a more predictable car. (all other settings very similar) . Now after trawling through various setups it would seem older ones went for thicker oils on astro, but some of the newer setups from this year prefer thinner like 7k & 3k. Could anyone advise?

2 - I have the rear skid plate on, how have others found it on astro?

3 - What is the affect of running the 4 or 2 rear brace?

Really is a great car and reallu impressed so far