Omnium cranks - roundness, chain run-out?

I just noticed today that theres noticeable change in tension with my set up when I have the chain tight, Ive not seen it before with normal tension.

anyway I tried different size chainrings, DA 7710 with an old and new HKK vertex chain, it was the same for each combination. binding for a quarter turn and loose for the rest of the rotation.

on the international scene I dont think Ive seen Omniums used, only 7710/SRM/Sugino 75 super/grand mighty, is this because the Omniums are not prefectly centred?

its annoying since Ive just invested in a full set of 7710 chainrings, and 2 sets of omniums. thinking about sugino grand mighty for next season, the square taper doesnt deform as much with them and they are rounder than 75's at not much extra cost.

other than that the stiffness and standard gxp bearings have been great

(just stating a few obvious things, in case they have been missed, feel free to ignore if you've done them)

Is the wheel straight in the track ends? This might cause a slight change leading to the binding. Similarly, is the cog on straight? If its slightly mis-threaded that change of angle could cause an issue

Most set ups are uneven to a certain extent, especially when new.
If it's not showing to be massively way out at normal riding tension then I wouldn't worry.

no problem, any suggestions welcome. the only thing I didnt change was the wheel and cog, it was defintely fitted straight, the hub is All City new sheriff and has large locknuts, the frame is Look 464p with thick track ends so its easy enough to get the wheel perfectly straight. the cog was almost new 15t 7600 DA.

Ill try again with a different wheel but currently all my wheels are built on Novatec made hubs, Ill have a 7710 DA rear wheel built soon and I imagine that would confirm if its the cranks that are the problem

ye its not really showing in actual riding, Im just obsessive with having everything set perfect/optimal.

loosen your crankring bolts, then jiggle your ring slightly, give it a twist by pressing firmly on the pedal whilst holding the bike still. This will help to centre the chainring on the cranks as well as possible. It's pretty normal for chainrings to be imperfectly roundish.

I'll just leave this here as well, in case you've overlooked it.
http://www.sheldonbrown.com/singlespeed.html#tension

loosen your crankring bolts, then jiggle your ring slightly, give it a twist by pressing firmly on the pedal whilst holding the bike still. This will help to centre the chainring on the cranks as well as possible. It's pretty normal for chainrings to be imperfectly roundish.

yep did that too. I tried with 49t and 50t lightly used Dura Ace 7710 and new 54t DA, those would have to be as round as you can get except for sugino super zen