dicnic,
There are many "drier"/light oil balls around with real cores.If you really can't find one that suits your purposes, bcw1969 is right in a sense. Many strong asymmetric balls can be drilled with the MB is such a position (usually close to the track area) that the backend is strongly reduced. The MoRich Mojave and the Solid LevRG, as well as a few balls from other manufacturers, have the potential to be drilled so as to have minimal, but sufficient backend to suit your needs. All it needs is a driller who understands both your delivery and asymmetric balls.
Also the backend of many symmetric balls can be reduced even further both by appropriate drillings and slip agent type polishes, such as Track's Delayed Reaction and Neo-Tac's Control-It.
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"None are so blind as those who will not see."