I have kids who will be learning behind my XLV very soon (they are 3 and 5). My 5 year old is already rocking the "Ski Trainer" and she surfs with me. I don't really see what difference going 14-18 will make behind say an OutbackV or an XLV, little kids aren't going to be "jumping the wake" to start, they are just going to get up and ride, so if you don't have a perfectly formed wake at 16mph, who cares. And all Vdrive boats (20ft or 23ft) are scary to a little kid with their loud, big motors. Lets be honest, at the start it's just intimidating for little kids to wakeboard until they get the confidence.

And when my kids are ready to start jumping, I am going to have them on a very very short line so we can go really slow and I can actually talk to them from the back of the boat to help them. I can't wait for this day.

Now for actual adult wakeboarding with Full Ballast, I have to agree with Yager97, 22 or so is where you should be riding. There is no reason to load up ballast for a big wake and then ride at 17 or 18. It's just not necessary, and if you have to ride that slow, you probably are still learning to jump and you are much better off learning on a smaller wake anways and a shorter rope. Watch old Wakeboard videos and see how big the guys go on those tiny wake and you can see that 2500lbs of ballast aren't necessary for beginners to be able to "get air". In fact a smaller wake teaches better form.