Hi joecappi,
Basically spread-loss is a back bet that eliminates negative P/L on a chosen selection, by increasing the potential loss on all other selections. In your example:
lay 10 @ 3.5 would have a spread-loss back bet of
the back bet, provided the price is 5.0, would be 6.25, as that is the amount needed to cover the liability of 10*(3.5 - 1):
6.25*(5.0 - 1) = 10*(3.5 - 1) = 25.
a) what is the correct condition for the "spread loss" ?
There must be a negative P/L on the selection.
what condition would i have to enter so that the spread loss equaliziation is not Zero but e.g. - 2 (or more generally, to accept a loss of e.g. 25%)
You would need to execute a usual back trigger, as the spread-loss is for zero loss only. The amount of the bet would be calculated as:
back amount = -profit_loss*(100-perc)/(100*(back_price-1))where
perc is the percentage of loss you want to leave on the selection, and
profit_loss is the trigger variable for the selection's P/L.
So if you have a loss of -100 GBP, and you want to accept 25% of loss, then for a back price of, say, 5.0 this formula would give you:
back amount = 100*(100 - 25)/(100*(5.0 - 1)) = 18.75 GBP.