No.
Given your camera sensor, you should be able to fit it within the aperture of the prism stem and avoid vignetting.
Firstly, the 8x8mm specs for ZWO's OAG has no meaning (except for trying to fool beginners). The aperture (hole) in the prism stem is the more important specs, and it is substantially smaller than the prism.
If you look at the drawings in ZWO's specs sheet, you will see this:
Notice that the aperture is 5mm by 7.4 mm, and on top of that, has R2 corners.
That being said, the ASI224 has a tiny 4.9mm by 3.7mm sensor and should be able to fit in the aperture if you orient the camera angle properly.
I just made up this quick drawing to illustrate:
The black rounded rectangle is the aperture of the prism stem, using ZWO's specs. The red rectangle is the camera sensor with the long axis of the sensor aligned with the long axis of the hole in the prisim stem. Notice that it sits inside of the black rounded rectangle.
The green rectangle is with the camera angle rotate by 90 degrees. Notice that it barely fits (read on to see why this is not neccessarily sufficient).
The blue rectangle shows a poor camera angle, with two corners hard vignetted.
Now notice the dotted black rounded rectangle. This represents the vignetting of the hole that is closer to the prism end for a small f-number. If you are using an f/15 optics, then you are closer to the solid black rounded rectangle. If you are using f/4 optics, you may be closer to the dotted rounded rectangle.
But, I think that in your case, if you orient the camera to agree with the red rectangle, you should be able to handle even short f-number.
This is not true if you were to use a ASI178 camera, where the sensor is a 7.4 mm x 5 mm rectangle. In that case, the rounded corners of the hole will always vignette that camera no matter how you orient it. An ASI174 is even worse, having a sensor that is 11.3 mm x 7.1 mm, and will severely vignete (you see a small circle in your guide image).
If you plan to upgrade your guide camera in the future, return ZWO's OAG to the dealer, since you will need to also throw away the OAG later when you switch to a better camera. ZWO really needs to replace the flawed stems with one that has a larger cavity for customers who already bought these OAG, since they don't work with modern guide cameras.
Chen
