The PET platform for experimentation with hpsg processing and implementation techniques is introduced. PET provides an extendible set of building blocks for the implementation of efficient processors. This enables straightforward comparison of different approaches, rapid development of new techniques and easy synthesis of known techniques. An overview of the basic design is given and key aspects of the implementation are discussed. Early empirical results on the three standard test sets for the LinGO grammar are given. Two improved expansion strategies are evaluated empirically. The results of fine tuning the quick check filtering method through empirical study are discussed as an exemplar of the proposed experimental approach to the development and optimization of processing techniques. An overview of the progress in processing the LinGO grammar made over a development period of three years is given.