Whats best when laying. A set stake or a set liability

My favourite staking (backing or laying) is to return 100 points
dependent on price.
Example: laying, say a 6/4 chance take 40 to lose 60 (40+60=100)
laying, say 1/1 chance, take 50 to lose 50 (50+50=100)
laying, say a 4/5 chance, take 55 to lose 44 (55+44=99)
etc, etc.
Nothing magical about it, and method of selection needs to be sound.

Thanks for the comments. That is what I am doing at the moment so I guess I am on the right lines

Surely liability? Otherwise depending on the value you lay the amount liable could vary from pennies to many thousands of pounds/

Kelly.

liability.

Lets face it, if you wanted to Back a horse in your local bookies' and the guy behind the counter asked how much you wanted to bet, would you say 'Oh, I dunno, you  decide'?

Or if you were backing walk into a bookie and say "I want to win £X, just take enough from me to cover that at current odds".

Doesn't really make sense.