Figured out why I was squeeking so bad - it was a bad reed.
That's sad, as this Legere Signature #2.5 is a new one I bought just 2 months ago. The other legeres I got did not seem to exhibit this problem, nor other reeds. Oddly enough, I got this new reed because my old reed had developed a crack. Playing the cracked reed on the V5 did not have the squeeks, but it did have an extra buzz to its sound.
Looks like next month I'll be getting a new Signature... wonder what happened to this one to cause it to fail, no drops or bumps :-/