Tab=1=18.5
2=15.2
3=13.2
4=12.0
5=10.5
6=9.1
7=7.9
8=7.2
9=6.1
10=5.6
11=4.9
12=4.4
13=4.0
14=3.8
15=3.4
16=3.7
17=2.8
18=2.0
19=2.9
20=2.2
21=2.5
22=0.0
23=0.0
24=0.0

Nothing sensational here the top 5 win 69.4% 0f races.

The top 5 win% win 67.0% of races.
The top 5 pl% win 67.1%.

What obviously does improve the s/rate is field size restriction.
Eg tab nos 1 say in a f/size of 4=35.6.
5=36.2
6=25.4
7=23.0
8=22.7

Tab nos 2 f/size 4=30.7
5=27.5
6=21.9
7-21.0
8=16.2
9=17.2
10=16.7.

Tab nos 3 f/size 4=26.5
5=17.5
6=19.5
7=18.3
8=16.8
9=13.4.

Whilst the s/rate improves the dividends only get lower so you lose,
unless you wan't to apply other filters that may make it profitable.

Hope this helps.
cheers
garyf.