I ran a R1 and a TZ250 together and found that the TZ made me faster on the R1. That has not helped me on the 600 though. You can do it, and like brownie says, it may not hurt you but it may not help you either. I found that the TZ was great for corner speed and realizing just how small a hole you could get a bike through. That really helped me on the big bike and to be honest I would like to be back on a big bike...I just feel more comfy on them. I ran my fastest times on the R1 with the TZ.

It can be done, and you will know rather quickly if it helps you or hurts you.