Hello!
Please specify what you mean by laying at SP.
Do you want to lay at SP before the start of the race using the special instrument of SP bets available on BetFair? Using this instrument, you allocate a certain liability, but you do not know what your actual bet size will be until the event turns In-Play and the SP becomes known.
If this is so, you cannot do this with these triggers because you will not be able to use the loss recovery plan. This loss recovery plan relies on the size of bet you are placing, and, as I said above, the size of bet is unknown at the moment of betting.
If you meant something else, please explain.