Constant speed or constant attitude?

I would like to hear what other glider pilots have found to be helpful
in trying to center thermals.

It is common in gliding books to read that a constant diameter circle,
as a product of flying a constant airspeed and a constant bank, is
important in centering thermals. If the airspeed and / or bank is
allowed to vary significantly the thermal circle becomes an inconstant
oval, which can make locating and centering a thermal more difficult.

I understand this, and I think it helps in staying in contact with a
thermal once I have identified the stronger area in a thermal and am
more or less centered in it.

But while I am exploring a thermal, while I am trying to get an idea
of how the lift is varying around the circle I'm flying, while I'm
working my way towards the core of the thermal, I find it more
informative to try to fly a constant attitude and bank and allow the
airspeed to rise and fall as the lift comes and goes, and not lower
and raise the nose in response to the airspeed changes resulting from
the lift changes. I find that flying a constant attitude rather than
a constant airspeed in this task greatly simplifies the task of
locating the stronger lift and moving to it.

If I do try to keep the airspeed constant by raising and lowering the
nose as I fly through the changing lift around the thermal I usually
end up behind the changes in lift and confused about the thermal's
structure.

By keeping a constant attitude while investigating a thermal I seem to
be better able to use the lift-created airspeed changes as markers of
the thermal's structure.

Am I goofing-up my thermalling this way?