We present several significant improvements in the implementation of the quick check pre-unification filter [7] [10], and the potential way in which the design of the quick check [15] [17] can be further extended. We analyse the effect of these extensions on LinGO, the large-scale HPSG grammar for English[14]. Althought these developments were done for the compiler system LIGHT [8], most of them are transferrable to non-compilation based systems.