We've had the same experience with sesame-- RAST was apparently a false positive, but we avoided for several years until we could look into it further. I know that the RAST score was over 4. Please note, though, that this is a child with MFA whose other known allergens elicited RAST values near 100 and over it, respectively.
We've also challenged hazelnut, which we have seen a positive RAST and SPT for (the IgE value was pretty low, though-- like 2-3 I think, which is "low" for my DD relative to her known anaphylaxis triggers).
However-- almond was in that same range, and unfortunately we've seen pretty serious reactions to cross-contamination from shared lines. So I'm not sure that the numbers on tests say as much as a lack of rxn history does.