Adjustable stem for a teenager bike?

I posted elsewhere about getting a bike for my 13 yo. He's having fun with it. :)

When we bought the bike, we suspected that he'd need a shorter stem, as he was rather stretched out on the bike. Everything from the waist down fits well (knee over pedal, seat height, etc.), but he's stretched out from the waist up. After one or two rides, he did decide that he's not comfortable enough unless he puts his hands up on the bars.

I saw an article that suggested an adjustable stem for just this situation - that it would better allow for growing room. Is this sound advice?

Here's the detail - Raleigh Revenio 1.0; 52 cm; 90 mm stem, and it's flipped such that it tilts upward. Not sure what the angles are on the stock stem.

I know we'll head in to get it fit properly, but I wanted to know what I was talking about before I do that. The place where we bought it said that stems ranged from $40 and up, and that the "mid range" would be $70. Again, I just want to make sure I'm knowledgeable when we go in.

(And in reference to the last thread, he is paying for the new stem.)

I would first ask your LBS (or your fitter, if they're different) if they will swap out used non-adjustable stems, either for free or for a nominal cost. Most LBSs have a bunch of stems lying around from other people's fits.

I'm not a big fan of adjustable stems, since you can't change effective length independently of effective rise. But it could be a quick and dirty way to deal with his growth spurt.