I'm glad that someone asks about those downstops. I have already built a couple of TT-02 and also got puzzled about the stops. If you built the Kit according to manual, the chassis is " wrong way wedge" - >way more ground clearance in front than in the rear, which is really odd imo. You cannot address with the stock springs as they are way too hard.
It gets better with the hop-up aluminum rear hubs, they have no downstops and because of that the ground clearance levels out between front and rear.
​​​Weird....