IDT the plaintiff's attorney's moral standing is a question. Both sides are going to say anything to win, since (despite, for example, New York Law) there is no enforcement of the legal requirement that attorneys may not offer frivolous arguments in favor of their client's position.

The plaintiff's attorney is going to claim that the track specifically solicited the attendance of unskilled (and therefore inherently dangerous) riders, who were compelled to sign waivers without physically examining the track, and that ordinary and necessary precautions were not taken.
The track's attorney is going to claim that the track's design and condition was exactly like other tracks, the riders were encouraged to examine the track, that their participation waived objection to the hazards, and the rider brought the sandbag with him (I'm almost kidding).

Not legal advice, just a thought: I have seen drivers/riders sign waivers with this printed under the name: "under protest". Legally it's worthless but it does leave the door open to future claims of objection.

I hope he loses, but it's probable that the track's insurance carrier will settle to avoid a very bad jury verdict ("any attorney who says that he can predict a jury verdict is an idiot").
What I'd like to see is a legal end to the "non-disclosure agreement" (we'll pay you if you don't tell anyone the amount or the terms) if public safety is an issue.