Many years ago when I first started flying I had a Falcon 56 (high wing) with dihedral. I eventually became rather good at handling that plane. It was 'predictable'. It could settle right in to the landing spot I selected.

When I then changed to a low wing with NO dihedral (constant cord) I DID notice a difference. The plane REQUIRED the wings to be consciously made horizontal. That is, when landing the plane did not 'settle' into 'wings level' flight over a given amount of time like the Falcon 56 did. I vividly remember thinking 'Gee, this sure is different'. And that was 20 some years ago! But then I always tended to notice things that others did not. I think that was because I liked to bring a plane in very, very slow (for a very short roll out) (like a bush pilot) and that is much trickier than bringing a plane in with typical, faster speed. So I was very sensitive to how the plane handled at very, very slow speeds. And at very slow speeds it was actually 'gliding in' under a little power, nose high (thus the wings were tilted up) to allow a smooth touchdown with minimal forward roll.

So maybe the dihedral is more noticeable at the very slow speeds and nose up conditions. This would make sense to me because in this situation the dihedral would attempt to act like feathers on an arrow. The odd part is that the faster planes I flew I built with the top of the tapered wings horizontal. This still introduced SOME amount of dihedral, but not much. I grew to like this type of setup because when I placed it in a turn it would stay there, even at very LOW speeds.

I have known many people that built their trainers with NO dihedral and had constant cord wings. Typical was the 'Sweet Stick'. They had no real problem learning to fly but they never landed at the extremely slow landing speeds I liked.

So I would not hesitate to suggest that you build the wing horizontal (no dihedral). Dihedral will not make a big difference to most people. Actually learning to fly using a wing with no dihedral will prepare the flier for pattern type and higher performance planes right from the get-go.