Did you do the measuring yourself? I've rounded down an mm when using the free spoke calculator. What do YOUR measurements give you? If you've got longer spokes, they may stick out past the nipple when you've got things all tensioned up, but it won't be that big of a deal if you're running some deeper dish rims. If you run the spokes too short, you may not be able to get enough spoke/nipple engagement. I've read on these forums you can go 2mm either way, but YMMV. Whenever I'm calculating spoke lengths, if find it very hard to vary my hub measurements to give me a 2mm difference.