Chris King?
Not sure about the 24h front, but the 28h rear they make. Why not get the best?
You might want to X-post this to weight weenies or something, btw. Let Nino regale you with his tales of dremeling every part on his bike, then ask him about light hubs. The guy is a walking bike encyclopedia.
I hope you don't weigh much, btw. 28/24 is not a lot of spokes for offroad riding. Find someone really good to do the build.
That makes me curious - how many spokes are people running? I've been happy with my 36/32 Chris King setup (on 390g road rims) but I suppose with beefier rims that spoke count could drop a bit.
-Walt