No record is perfectly flat. But the kind of warps can make a difference. If the warp is way below the tonearm/cartridge combination's resonance frequency, there won't be any problems, apparently as is the case with the singles you aquired. So, in general, a very high compliance cartridge mounted in a rather heavy tone arm, will lead to problems at certain, often very small and sometimes hardly visible warps. The gently up and down movement will, however, cause only minor problems, if any at all. So, in general, high compliance carts will need a light tone arm AND state of the art bearings with very low friction AND NO PLAY!! This is the very reason high compliant carts can be used (of course, within the tone arms specs!) in the Technics SL-1200 series. Its tone arm is not that light, but light enough to take a wide range of top class carts. All because the the total package is top quality.