My 16 y/o son did superb last x-country ski racing season.
He would like carbon skate boots and I am dizzy researching everything.
Can someone rec. a good pair?
Ditto. It sounds really blunt but the best way to find boots is to go to a shop and try. Everyone is a little different.
I'm not a X-C skier but the same system applies for running shoes, alpine racing, and just about anything that gets strapped to your feet.
Xc boots are a bit different then alpine, so yes you can basically do this by mail, even though you can basically do same also for alpine, if you have some boot fitting knowledge... not what most "boot fitters" understand as boot fitting, but knowledge how to modify outer shell to fit your feet (yes I'm waiting for all the flames toward me now :) )
Anyway back to original question... are you sure your 16!!! years old kid need 500eur boots? Really... WC races were won with "normal" xc boots for 250-300eur still this season, so for some 16 years old kid, 500eur boots (which last 1 season, or less with serious racing) is "a bit" expensive I would say. Otherwise what would be good pair... there's not many options... Alpina has them for racing service since middle of last season, and will be probably publicly available in stores for next season. Fischer has them publicly available since middle of last winter, Madshus has them for some 2.5 years now. That's basically all you can get in this range for Rottefella NNN bindings. Then it's Salomon, which is currently only one with carbo model of their skate shoes for Salomon bindings. Most likely there will be another company or two coming out with carbon version for next winter also for Salomon bindings, but at the moment Salomon is only one.
Now what's difference between "normal" and carbon shoe... It's few grams lighter, and literally just few grams. Definitely not worth paying twice as much for it because of those few grams (not 100g or 200g, but really more like 20g). It's a little bit stiffer then normal one, even though current ones are stiff enough with carbon inserts in boot sole. And it looks a little bit slimmer, even though it's hardly the case with current shape of race boots. I'm using Alpina ESK pro skate boots for skating, and I had chance to test their new Elite 2.0 boots last season (their carbon skating boot), and even though I have spent most part of my life xc racing, and have really great feel for skis and equipment, I honestly didn't notice all that much of difference between old and new boot. Main difference is cuff, but that's due to different shape, not carbon, as old cuff on ESK Pro was already carbon. So honestly, I would suggest to look for non-carbon race boots, as they are almost half cheaper. As I wrote, all current carbon boots are in range of 500eur in stores, and probably Alpina will be somewhere there too, while non-carbon race boots are around 250-300eur. And only difference between carbon and non-carbon is sole, which is all from carbon on carbon boots, while it's plastic reinforced with carbon on "non-carbon" boots. Cuffs and upper parts were from carbon before already even on "non-carbon" boots. Also size and shape is same. 43 with ESK Pro is exactly same as 43 with Elite 2.0. So if you take boot from current company, size will match.