What should an odds line be? For easy reference; part of your posted reply.
The higher the rebate, the higher the percentage of whale money at the track.
About 34% of total win pool at tracks like MNR, CT, DED, etc.
About 10% of total win pool at tracks like SA, CD, etc.
The higher the rebate, the greater the percent of pool that shows up after the gate opens.
About 60% of total win pool at tracks like MNR, CT, DED, etc.
About 45% of total win pool at tracks like SA, CD, etc.
Using that math, for every $100 wagered "late"
$57 will be whale money at tracks like MNR, CT, DED, etc.
(34 / 60 = 56.7%)
$22 will be whale money at tracks like CD, SA, etc.
(10 / 45 = 22.2%)
CONCLUSIONS
The pools at high rebate tracks have 2.6x the percentage of whale money LATE!
($57 / $22 = 2.59)
Since that money is (effectively) in the hands of JUST FIVE BETTORS, the pool swings will be FAR MORE VOLATILE at higher rebate tracks.
(Meaning: When they agree, you can easily see 4/1 become 4/5.)