Start with the easiest to modify - dump all weight possible. Depending upon your average weight that is quite a lot of ballast in bodies. 8 people *165 = 1320 lbs; that is more than the stock ballast of the X-15. So take just the min (driver, spotter and yourself), 3/4 tank of gas and dump other stuff not needed. The 215/X-15 has quite a bump even with no ballast but why stack the odds against you to start with.
IMO, wakeboarding at slower speeds with a helmet on would be less chances of injury than 30 MPH on a ski but then again I speak from no experience on the (water) skiing side of things. Take the wakeboard out at 19 MPH with longer rope and enjoy some one wake jumps, surface spins, lip slides etc. The water is much softer at 19 MPH. I think the problem people get into with wakeboarding is to expect the boat (speed) to make up for deficiencies (I speak from experience there) in skills thus taking harder falls.
All in all, whatever it takes to get out on the water and have fun rather than bad experiences. I'll look forward to reading how you progress on this.