BFSP volatility...

Bets	Wins	Win%	P/L(SP)	race%	ROI SP	P/L BF	ROI BF	AVG Odds BF	BF A/E	BF CHI	BF EXP WINS	AVG BF WIN ODDS
20302	1022	5.03	-3626.25	6.83	-17.86	3365.8	16.58	37.67	1.15	20.42	890.17	23.61

Amazing on paper in reality taking part even at really low stakes probably cannibalises the edge by shifting down the BFSP?

I think it would very slightly.Each horse is treated individually.

There was a thread on Bet Angel where someone said that increasing his greyhound SP bets from £5 to £10 took away his profit margin.

Thank you JML

I would imagine that in those markets even pretty low 5, 6/1 shots are extremely volatile.

so it's hugely profitable @ 22s avg odds but loss making @ 18s...shows you how important every tick is

generally I would prefer not to be on at all rather than take an unsuitable price or chance a favourable BSP

I think there is very little chance any additional bet would not affect the BSP to some extent, because of the way it is calculated.

As to "how much?" - there's a question.  Looking at a similar market and runner to the one you suggested in today's racing - 1335 Ayr Bray Dale - there was £144 of backers' money at a BSP of 34, so you might expect placing a £1 back bet would shave about a quarter of a point off the BSP, but two things will act to counter - BSP layers seeing better value as more backers' money is shown and so betting more, and more Exchange money getting swept into the calculation as the implied BSP drops.