The method Dave described is what I normally do in my LS-3a. Yesterday
I was trying some different settings and noticed that at 100 knots,
the flaps could be moved between 0 and -7 with no issues. At 120 knots
the flaps wanted to stay at about -3 and when I moved them to -7,
which required some pressure, it created a humming noise. Seems that
-7 should be better at higher speeds but the noise and pressure on the
flap handle tells me otherwise.

Also, the LS-3a Flight Manual has the following instructions:

Up to 103 knots - Flaps should be between 0 and -7, depending on
desired speed. Once the aircraft is trimmed for thermaling, no
additional trim adjustment is required for high speed flight. Any
stick forces can be removed by adjusting the flap position. This
results in the correct flap position for all speeds.

103 ~ 146 knots - Flap position -7. Stick forces should be reduced to
zero through trim adjustment.

All the best,
Steve

Dave Martin wrote in message ...

snip

When cruising I put the flaps in whatever position
feels comfortable with little reference to the ASI,
other than to monitor the chosen cruise speed. The
way to do this is quite simple, once you start to increase
speed move the flap lever into the free position and
without letting go, let it float. You will find that
it adopts a set position which can be felt, for a given
speed, then you can drop it into the closest notch.
After a while this becomes automatic.

snip

Dave Martin