Is a ring/cog chainline delta of 5mm a bad idea?

I've been looking to build up a fixie and the IRO group buy has put me into the mix.

I have a Bontrager Race Lite GXP crankset (double) that I would like to use. The chainline is listed at 44.5mm and I assume this is measured between the rings. Assuming a ring spacing of 5mm this gives a chainline of 47mm / 42 mm on the inside / outside. Most fixie hub/cog combinations look to have a chainline of 42mm (with a rebranded novatec or formula hub). Assume now that I am anal and I want to mount the ring on the outside for a clean look. This gives a chainline delta of 5mm.

The IRO geom. spec gives a chainstay length of 391mm (don't know if this if BB center to dropout center or whatnot). With fancy math I get an chain angle of 0.73 degrees [ arctan(5mm/391mm) ]. With this angle it looks like i'll be losing 0.01% power [ 1 - cos(0.73 degrees) * 100% ]. This doesn't seem like such a penalty...

I see chainline mentioned a lot here.

How important is it?

when does the delta get bad?

Having an OCD moment... tom.