Wing tip stalls

Common knowlege about Glider wing designs says that a high taper ratio will
lead to Wing tip stalls.

However in our flights and research we have found that a straight or forward
swept flying wing will not stall a wing tip despite the very narrow chord
( renolds numbers of 325,000) and lack of washout at the tip. I can attempt
a stall in the Pioneer IId by bringing the stick slowly all the way back
giving a CL of about 1.5 at 32 mph. We do have some separation at the root
but there is no sudden wing tip stall despite no washout at the tips. The
glider itself will not stall.

In the gliders I also fly with tails, Grob 103 and 102 there is also a
reluctance to not stall a wing tip but that is perhaps due to the washout at
the tips.

Does the wing tip stall suddenly in some of the high performance ships that
may not have the amount of washout that the lower performing ships? What
gliders if any do stall a wing tip easily?

-mat