Don't worry about the second O2's. You can definately install the MIL's and zip tie them up out of the way. The ONLY purpose of the second O2's is to verify that they cats are in place and operational. If you install MIL's, the computer is fooled into thinking the second O2's are saying that the cats are there and working.
Another option (which is what I'm going to try when I do my longtubes in a few years) is to not install MIL's and simply tie the second O2's up out of the way. The O2's would then function by sampling the outside air rather than the exhaust. The result? The first O2's measures the (I think it's the CO) content of the exhaust. The second O2's remeasure the content to see if it's lower. The job of the cats is to make the exhaust burn clean and expel H20 and CO2. By sampling the outside air with the second O2's, the computer will think the cats are 100% efficient.
Keep in mind that's just a theory (if you use MIL's, it REALLY doesn't matter where the second O2's are located because they don't do anything at that point), but it won't cost you anything to try it. Even if it doesn't work, the only thing that will happen is a check engine light with come on and a code will be set in the computer. The computer only uses data from the first O2's to adjust A/F.
Hope this helps!