Among others, refining the methods of [Fortnow and Santhanam, ECCC Report TR07-096] we improve a result of this paper and show for any parameterized problem with a ``linear weak OR'' and with NP-hard underlying classical problem that there is no polynomial reduction from the problem to itself that assigns to every instance x with parameter k an instance y with |y| = k^{O(1)} \cdot |x|^{1-\epsilon} unless the polynomial hierarchy collapses to its third level (here \epsilon is any given real number greater than zero).