Originally Posted by you
yeah they're a mm different, thanks.
should the spokes be of equal tension?
If you go to the "Calculator" page of that spreadsheet, you should see an entry over on the far right (in the Rear Wheel group) that is labelled "Tension L/R". It should give you a ratio (in %) of the left to right sides (or non-drive to drive sides). As I stated before, OC rims don't eliminate dish, they just reduce it. This allows for the tension on the non-drive side to be higher than a normal rim. A normal rim will usually produce a ratio of ~60%. I would speculate that the tension ratio for your OC rim will be in the 85-90% range (again, just my guess). The closer you can get to 100%, the better.
To specifically answer your question, no, I don't think they'll be the same.
So, what is that ratio?
A word of caution here... I have found that ratio number produced by Spocalc to be a nice guideline, but it's most important to tension up the drive side spokes to the rim manufactureres max specification to get the strongest wheels. Get them all tensioned up and then you can finish your truing and dishing with the non-drive side spokes. I just check them to make sure there is not a spoke that is much differnt from the rest - and, I have built wheels that this happenned to me. One spoke would be way loose and the wheel would seem to be done. In this case you tighten up that spoke and re-check everything else. Don't get hung up on the tension for the non-drive side spokes. Just make sure there are no noticeably loose ones. Concentrate on the drive side spokes. They are doing the "heavy lifting" for your rear wheel.