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Hi Glen,
this is actually to your advantage, believe it or not.
With two uneven vanes, you'll be able to give the secondary an off-set that will actually increase the amount of light efficiency to your camera.
As the 'cone' of light comes up to the secondary from the primary, the geometric shape it hits the sec at is not an even one, rather more pear shaped, fatter at the bottom, narrower at the top. The bottom part of the secondary can actually miss some light. This 'off-set' is a setting of the secondary so that it is more efficient. With a visual scope this is not so critical to get right as our eyes won't really register the few % difference. But with photo, this adds up quickly.
The off-set of the secondary is both back away from the focuser, and up from the primay. But if you just set it back, this will give you the majority of the light gain advantage. It is no more than 2mm in either axis.
From your post, I have a couple of questions. The orientation of the vanes, is one of them in line with the focuser? That is, is its anchor point where the focuser is? This will set two other vanes perpendicular to the focuser, and the forth vane is an the far side. If this is the case, it is easier to accommodate the off-set. Next, the length difference in the vanes, are they longer or shorter? As two vanes are the same length, they would be set perpendicular to the focuser. It is then a simple determination of which vane will go where to push the secondary mirror away from the focuser.
There are several sites that are 'off-set calculators'. A quick search will pull them up.
Alex.
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