I have both the 5T diopter and the 5505 standard port for the 60mm. I'll go home tonight and try it to see if it fits. My suspicion is that it does fit, I think there is some breathing room in that port.
However, I would try to dissuade you from using this combination. Depending upon your subject you may not be able to get close enough to use this effectively. The 60mm already focuses very near the lens ~8in. With the 6T diopter, your far focus will be very small and limit the kinds of things you can photograph severely. The high end of the magnification that you get with the diopter will be very difficult to use and the low end that you can use will be what you could still get without a diopter. With space for ports etc you might not be able to focus on anything very far out, or you'll be spooking it with the port. You will definately have trouble lighting it.
A much better solution is the 105mm macro with the 3/4T diopters. This gives you a little more breathing room to push it with diopters. Martin Edge talks a lot about this combination in his book. I have a custom Ikelite port to accommidate the 4T diopter on the 105mm.
Photography is art and experimentation is key so do what you want to make great pictures. But the 60mm is much better as a medium size reef fish portrait lens than a true macro lens. The 105mm and longer lenses are better for grabbing the truly small stuff.
A 60mm with a teleconverter for 2x magro would be interesting however.