I haven't ran losi tires in a while. But I rememebr they always needed to be cut to fit the wheel better.
The insert is a tuning tool. You can cut it. Or stuff the whole thing in there. It was stated on here somewhere. Maybe start with about a quarter of it cut off. Then on the next set, you can go from there.
Not sure about the next one. Are you asking about 2Wheel tires on the front of 4Wheel?