G'day Sandgroper,some interesting figures you posted for Perth racing.Here are some figures(albeit from 5 years ago)for races Australia wide.Based on the figures you posted,I imagine they would still be fairly close to the mark today.
TAB No.1 19.5%
TAB No.2 12.8
TAB No.3 13.4
TAB No.4 7.5
TAB No.5 8.9
TAB No.6 7.3
TAB No.7 5.5
Interesting to note that from these numbers comes a staggering 74.9% of winners.
Some figures on days since last start:

Within 7 days 30.2%
8 to 14 days 37.0%
15 to 21 days 19.0%
22 to 28 days 5.0%
29 and above 8.8%
Note that 86.2% of all winners had their last start within the last 21 days.

Old figures I admit,but definitely food for thought!
cheers