Aussie entertainer Rolf Harris may have had it right when he wrote the song My Boomerang Won't Come Back. Most of them don't, reports Canada's boomerang man,John Cryderman in the Vancouver Province. For the most part. he says'', Austrailian boomerangs are too heavy and don't generate enough lift. But the former cop turned professional wood-worker and boomerang expert from Chatham. Ont., says he can fix them. "If theyship them to me, I'll retune them and then the suckers will fly." he said. lf that basic truth doesn't hurt in itself, Cryderman, in Vancouver to organize a woodcraft show, has more. Australia's aborigines didn't, as most Aussies believe, originate the aerodynamic missiles, "The earliest recorded boomerang was discovered where Poland is now, 23,000 years ago," he claims.