Are you ever TOO big for a water slide? My answer would be HELL NO! However, this video may prove me wrong.
Someone outside Austin, Texas has a pretty sweet waterslide on their property . . . it looks good enough to be at an actual water park. But a guy was going down it recently when he flew off the side . . . fell about 15 feet . . . and landed on ROCKS.
Luckily he survived, but he ended up with a broken arm, several broken ribs, and lots of cuts and bruises.
https://www.facebook.com/jamesdavidsalmon/videos/10107892394420190/