Gotta be low pressure. I dunno how you could ride it with 20 pounds in the front.
Any less than about 32 in the front of my ol' Superglide and it feels real doughy in the front end.
I'd put money on one thing DJP, if you told Metzeler you were running 20psi I bet they don't shell out for a replacement.
Not trying to be too negative, just sayin'.
Roo