I have a fleet and we take people out all the time. We give them a verbal claim but nothing more. the reason being that anyone may try at anytime to make a claim, doesn't mean that they actually have a claim. There are many levels of looking at this, from inside the box, i.e.: like most of the sheeple IN the Matrix, or from outside which is what I rely on and which will probably be waaay too far out for you.
Firstly, you could write a waiver for people to sign who ride the sled. Not too difficult, just use one from the local ski hill or go gart track as an example. This of course does not prevent anyone from actually making a claim, just that most will operate under false assumption that they are under contract and cannot. None of which is true of course unless the waiver were written in the correct sentence structure and consideration given. (
www.dwmlc.com) NOTHING is!
Someone could go to a LIAR and file a claim regardless of what you do, and you might be able to use the waiver as a defense and maybe get away with it. Then again, maybe not. I never defend as defense never wins is almost a universal rule, think football! There are other ways, "in the box" so to speak and some work okay but never with any guarantee. Which is why I prefer using the knowledge I have outside the box, and vacate their claim as perjury via fraudulent conveyance of language. (it ALL is if written in adverb-verb)
So in summation, whilst the first suggestion is the simplest, the fact of the matter is that the only guarantee is either avoid the risk altogether, or have the knowledge to vacate any claims as they may come. I chose the latter as it not only protects me from frivolous things like this, but from ALL LIARS, IRS, government or otherwise. Ignorance may be bliss, but knowledge is POWER. Good luck. G.