Only on my own experiences, but with foams...
I use a regular ta05, with 3racing graphite chassis and towers/trf shocks, and have used it with soft foams indoors with a relatively average spring rate.
The stiff chassis makes the car transition left to right quickly, the soft foams give the car its grip. So combined, you have a car that can be placed anywhere on the track, has excellent low speed grip and with the right gear ratio, you are dialled
The stock '05 chassis is too flexable for ideal use with foams if you want to be at the sharp end of qualifying.
So, A Stiff chassis with Soft suspension and soft foams is a no no.
A stiff chassis, with average suspension and soft suspension will find the apexs better but may feel like it will tip if you're carrying too much speed into the corner, as the spring rate is allowing it to work a little too much.
So, in essence you might find a stiff chassis, with hard suspension and soft foams better but that may scrub the tyres up too much, or tip it over.
Trial and errror, get the laps in and see what feel is best for you. 3 hole pistons are a good starting point, as is 40wt all round on yellow springs if you need one.
If all else fails and you have to, use what you know is good