Thanks for the fast reply =)
Using the coords you suggested it looks very similar to the picture in the first post
As you can see, it's still outside the inner circle texture.
Fiddling with the coords a bit more, I got the following result, using the following coords: 0.03, 0.97, 0.03, 0.97. However, here it is inside the inner circle texture, but there a black bars on the edges, as it appears only the corners are round.
I've attached the entire file as it is currently (it does have dependencies I haven't attached, these however have nothing to do with the inner content).
As for SetTexCoords working with SetTextureToPortrait:
It is a bit hard to describe. It seems as if the rounding done by SetTextureToPortrait is in relation to the size of the original texture, and so is the work done by SetTexCoords, giving the result of only rounded corners, not a perfect circle. This is the case no matter the order in which SetTextureToPortrait and SetTexCoords are called. This can be seen in the first picture in this reply.
What I would want is to call SetTexCoords to crop the borders of the pictures, and taking the result hereof and marking a circle out of it. This does not appear to be how these two functions work though.