You took the words right out of my mouth. My experience as been this...
When I hatched out my once-in-a-lifetime surprise pied clutch last year, both both dame and sire had STRONG het pied markers.
This year I hatched out approximately 30 50% possible het pieds, males and females. About 1/2 of them had makers.
I don't see these two bits as coincidences... Plus I'm not going to name drop, but the people who would know more than any one, place a tremendous amount of significance on the markers. On a side note, there is more to markers than just the belly. and for the record I wish there were no pied markers.... seriously...
I will agree with the above posters who say its not a 100% indicator. I'll be hatching out at least 4-5 clutches of 100% het pieds this year and I'll post how many have the marker... That's information I've wanted for a while.
Justin