Frozen Leaf

This is my first photo taken with my reversal ring. I am not sure what I'm doing wrong, but there's pretty severe vingetting [cropped out here]. I'll be playing around with it some more until I figure out what's going on; if you have any ideas, speak up. The lenses I used were both Minolta 35-80mm zoom; am I supposed to use a prime lens? I noticed that when I coupled one of the 35-80's with a 100-300 with the larger lens attached to the camera, there was no vingetting at all... but it was near impossible to get a focus on anything. help.