Siemens S7300 software redundancy

Anbody ever used S7300 with the software redundancy blocks FC100, FB101 etc? I am told that the declaration of IEC timers and associated DB's, MB's etc must be contiguous. Does that mean that there can be no gaps in the use of these DB's etc? For example if I declare DB's 20 - 40 for use with the IEC timers,in FC 100 but only use half of them in the redundant software, would I get an error? The same question applies to the use of MBits. Siemens are are a little vague on this to say the least. If any one has had experience with this I would really appreciate the benifit of their experience.
Thanks in advance

I can't help you and will look for the answer but when we had to do our first redundancy:
After few bad try with the redundancy kit, we choose to do it by ourself with a 2 DP plc using a MPI connection to check plc health and the other on Profibus to read a remote i/o rack common to both plc.
I did 3 others like this in the past 2 years that serve me well.

You had to manually copy the usufull data to the slave plc and being ok with a 2 seconde for CPU switch but over all it was just fine for the application.

There should not be any problem if you don't use all the DB and M flags. The redundancy blocks will transfer all data from DB 20 - DB 40 and it will effect your switchover time as more data will have to be transferred.

I have tried this with Mbits but not with Data blocks. I would create all the DB from 20-40 in my program so that the redundancy blocks can find the DB when it is trying to transfer to the other CPU.