Much better
You really should look at getting a field-flattener. The WO 0.8x that Rob (turbo_pascale) and I use is great - it doesn't eliminate ALL seagulls but most of them.
Problem for you might be that it's also a focal reducer, when you wanted MORE focal length not less
It turns our ED80 into a 480mm f/6 instead of a 600mm f/7.5.