Rows per block can be a bit complicated. There is a whitepaper on PSDN.
If an area only contains indexes use a RPB setting of 1. For type 2 data areas and assuming that you haven't modifed the create & toss limits:
ProVersion: 10.00
BlkSz: 8,192
AreaType: 2
SAFR: 7,958
From To iRPB
----- ------ ------
1 28 256
29 59 128
60 121 64
122 245 32
246 495 16
496 992 8
993 1,987 4
1,988 3,976 2
3,977 1
ProVersion: 10.00
BlkSz: 4,096
AreaType: 2
SAFR: 3,862
From To iRPB
----- ------ ------
1 12 256
13 27 128
28 57 64
58 117 32
118 238 16
239 480 8
481 963 4
964 1,928 2
1,929 1
Blocks per cluster. OTOH, is largely a matter of taste. My taste is to use 512 for all non-trivial type 2 areas and 8 for type 2 areas that have very small amounts of data.