Not possible for the condenser to be the problem. It sits ABOVE the negative carrier, and cannot interfere with focusing. Whether or not you'll get even light output from center to edge is a different question, and I can't answer that without having seen the setup. Sometimes condenser sets designed to work well with a lens of a given focal length will be okay with a lens of a shorter focal length - sometimes not. It doesn't work the other way around. Chances are good that you need the recessed tub that has been mentioned here already.