I'm still deciding what to do ... but in the meantime I have a couple of basic dutch betting formulas for anybody who is interested in having a dutch bet.

To win a set amount on each bet -
p = the percentage chance of each runner, all added together
m = our multiplier

m = (p/(100 -p))+1

example.
we want to back 2 horses, 1 paying $5 and the other paying $10. We calculate the odds chances of each, so for the $5 chance it is 20% (100/5) and the $10 chance it is 10% (100/10). So our p value is 30 (ie. 20 + 10). The formula becomes -

m = (30/(100 - 30)) + 1
m = (30/70) + 1
m = 1.43

to calculate the bet amount for each bet we multiply the horse percentage chance by our multiplier (m). So the bet amounts are -

a) $5 horse = 20 * 1.43 = $28.60
b) $10 horse = 10 * 1.43 = $14.30
Total amount bet = $42.90
***NOTE these amounts are calculated to win $100. If you would, for instance, like to win only $20 you would recalculate the bet amounts by using the formula ((b/100) * bet amount) at this stage, where b is the amount you want to win.

If horse (a) wins we collect 28.6 * 5 = $143
If horse (b) wins we collect 14.3 * 10 = $143
minus the $42.90 outlay and you have a net profit of $100 if either horse wins.

Next time I will discuss the formula for betting a set amount on a race. I have run out of time for now.