John,

For what it's worth, I don't think this is a good idea. You may not
have a choice which way you thermal, especially if you join others. If
you have concerns about maintaining proper airspeed in the pattern, I
suggest the following: at some fixed altitude well above the IP,
increase your airspeed to pattern speed and maintain it while you make
your way to the IP. Even if you decide to stop and test a potential
thermal, keep flying at your chosen pattern speed. If you decide to
stay with the thermal to extend your flight, then slow down. If not,
keep up your speed. This will attune you to the sound, feel, and pitch
attitude of the glider for several minutes prior to enterning the
pattern.

If your IP altitude is 700 msl, you could increase your speed as soon
as you descend below 1500 msl. And remember, in the pattern, you
should be checking your ASI often, at least once every 7 seconds. Any
variation in speed should be addressed immediately. If your speed
varies more than + or - 5 knots, you should take a refresher flight
with an instructor. There's no shame in sharing a flight with someone
who can help get you back in the groove more quickly.

OC