Does 10 degrees of flap have any real effect on braking efficacy?
Theoretically, it depends very much on air speed, if we are talking simple SEP.
In very round numbers, reducing flap by 10 degs means reducing angle of attack by 1.6 degs or less (1/2 x 1/3 x 10).
Lift=Weight at stall speed at maybe 20 degs, so 1.6 / 20 x Weight = 8% of weight, and braking friction depends directly on weight. If you are right at stall speed (ie about to take off) then 8% over 0% makes a very big difference.
At 80% of stall speed, (Lift=64% of weight), 1.6 / 20 x 80% = 6.4%, and 6.4% over 36% is a significant fraction, but if you aren't that fast to start with and also as you slow down, it soon becomes irrelevant.
Personally, I feel a pre-flight look at the surrounding fields in google earth is sadly under-recommended.
Otherwise, absolutely no comment on anything anybody else has said. At all. <retiring to shelter>