Thank you everyone, for the comments and suggestions.

Urban Knight, I feel much better knowing you have the same rims as I will have. I was nervous about durability for my weight, but it seems like I'll be okay.

I am in fact going for a very light wheelset on a budget, but I"m not opposed to using Brass Nipples.

From what I've been reading, it seems like it's actually not the best idea to round up? Should you round down? Or rather, it'd be easier to fix the mistake of the lengths are slightly off if they're a bit shorter rather than longer.

My plan now is to go to the shop tomorrow when I have the rims and hubs and talk to the wheel builder personally and show him my measurements. If they have the supplies I need, I'd be happy to buy them from the LBS (unless they're ridiculously over priced....), if not, I'll buy what I need and return with everything for them to help me out.

Hopefully they're accommodating. I haven't been to them before but they're recommended as being good wheel builders here in NYC.

Thanks again everyone