I am doing a budget commuter rebuild on a Panasonic DX-2000, which is coming out great (brush painted with rustoleum and it looks fantastic!), but I am rebuilding the old Arya 27" wheels/Shimano high flange hubs (no model name/#) and having a bear of a time with spoke lengths.

The problem (pre-disassembly) was that the rear wheel was impossible to true. As close to true as I could get it (which was still unrideable) half the spokes were under very low tension and half were very high...so I took everything apart and determined that I would rebuild it with different spoke lengths for the rear, and just go ahead and do the front with it using the same spoke lengths.

Spoke length calculators are confusing the heck out of me, and it doesn't help that I don't have a computer at home for quick reference. I gave up on them, and instead my question is this:

All of the spokes on the rear wheel were the same length (310mm), so would it be reasonable to guesstimate a shorter length for half of the spokes and rebuild it that way? E.g., 310mm for half and ~305mm for the other half?