Wild Willy 2 Damper Oil Advice

[namfreak 0]

On the good advice given on this forum, I decided to "Hop up" to the Tamiya CVA Super Mini Shock 50746 set for my Wild Willy 2.

The damper oil include in the kit is clear, so I'm guessing it's 900 grade "hard".

I used the stock yellow damper oil (400 grade? - soft?) in the rear shocks of my Hornet re-re.

Assuming I'm going to be using the WW2 "off road" on grass, dirt and sand, what oil grade (soft / hard) do you think would be suited to the WW2 chassis and the CVA shocks?