For a namedtuple such as turtle.Vec2D there is no significant difference in the time of unpickling. But for simpler type it is.

$ ./python -m timeit -s 'import pickle, turtle; global I' -s 'class I(int): pass' -s 'p = pickle.dumps([I(i) for i in range(1000)], 3)' -- 'pickle.loads(p)'

Before: 1000 loops, best of 3: 1.6 msec per loop
After:  1000 loops, best of 3: 1.82 msec per loop

So I withdraw my patch. Unpickling performance is more important than pickling performance, and status quo wins. Sorry for the noise.