Is the insert completely soaked?
Ifso, i'd say it's a absorbancy issue. You need more stuff'n...I have bought a dozen 3layer hemp inserts from jamtots and they rock
I think a 2 layer would have been more than enough though...doh!
Ifnot, you either have repelling or fit issues.
repelling, scrub the suedecloth with dawn and run through your washer until you have no more suds. If you have hard water AT ALL, you might consider getting some calgon water softener (looks like fabric softener, get it at walmart) which helps remove soap buildup.
because wonderoos are "one size" you need to tinker with the stuffing sometimes to get the fit just right. I've had more problems when he was littler and I was trying to use too thin of a insert. You might consider a doubler/extra bulk between the legs to pad out and fill in the gaps more, or try a *thinner* insert and a smaller rise setting...
Let us know how it goes!!