Heart rate zones

Hi there
I just bought a heart rate monitor PolarF6, is anyone familiar with this model?  So many questions....

I was in a cycle race the other day and used the heart rate monitor - according to the preset zones I was in the range of 88 -95% of my MHR.   My question is if I am to be training in my light or moderate heart rate zone, the level of effort doesn't seem very high.  (The MHR is age based calculation)   I seem to be able to sustain the excercise at a high heart rate over a reasonable period of time, but I know that you are not supposed to train anaerobically very often.   So what are you supposed to do - train at your usual level which is often at a high heart rate?  Or do you drop your intensity so you are in a lower heart rate zone and feel like you are not doing enough?

Also, if anyone has this model of HRM is there any way of setting up your own preset heart rate zones -  I can't find this info on the web

Thanks!