First of all, I should come clean: I'm cross posting this here after not getting an answer in Bicycle Mechanics.
I'm looking to build up a wheel with an internally-geared hub to occasionally use on my fixed gear Cross Check for light touring. I hope the mention of internal gears doesn't generate a lot of boos! I'm going to keep the bike fixed for everyday use, but this will allow me to ride the same bike on tours. I've been intrigued by this as an option for quite a while.
My calculated spoke lengths from Damon Rinard's spocalc.xls spreadsheet are 283.8 and 283.2 mm for the left and ride sides, respectively. I've read and been told to round DOWN, which would ideally indicate 283 mm spokes for both sides.
I got a good deal on spokes from Nashbar, but they only had even sizes and I rounded all the way down to 282 mm.
Is that too far, i.e. will I not get enough thread engagement in the nipples?
I plan to start building tomorrow for a multi-day ride starting next Saturday. If these spokes are likely to be too short I can get some 284s from my LBS. My guess is that a mm below ideal is still fine, but if I need to bail on these spokes I'd like make the decision before I open the packaging so I can return them.
Thanks for your time,