two layers of 200 wt mm fleece wouldn't work for my super soaker (tried it) but ya never know with fleece, everyone has such different experiences.
it sounds like your guy's got a really fast urine stream.
Have you tried an aristocrat? I suggest this because they sort of fit like shorts and give nice upper thigh coverage.
Are you absolutely sure that your diapers don't have detergent/mineral build up?
Can you remind us what types of diapers you've tried. Sometimes I think hemp doesn't absord as fast as cotton, maybe try using a nice thick, well broken in, trifolded hand towel as a doubler. Something soft and plush that will absorb fast.
HUGS, supersoakers are hard to CD sometimes.