I have put a 120 on my mc-18 I think it screws up the profile of the tire. The NSR wheel is not wide enough for the 120. I went back to 110. You should be able to find good tires in a 110 front and 150 rear. I have the Michelin pilot power race h2 on my mc-18 I used it at a trackday great tires. I think Michelin has up graded this tire to the new dual compound tires. If you want slicks you need to contact a race tire distrbuter as most shops can't sell slick (in the States) They can also recomend tires that will fit you rim width.

On my mc-21 that I have not taken to the track yet it will be running a 120 front 160 rear. But it has a CBR600 front wheel which is wider than the stock NSR wheel. I Guess i should take both bikes a see what the diffrence is
Hope this helps
Steve