This paper describes an efficient variation of a well-known technique for converting a general-purpose analog computer (GPAC) to a chemical reaction network (CRN). If an input system has n variables, the existing dual-railing technique requires 2n variables in the resulting system. As the resulting CRNs are often fed into downstream processes which may themselves be exponential in the number of variables [7], it is frequently worthwhile to try to minimize the number of variables generated in this conversion. This paper presents a technique that results in fewer than n new variables, by rewriting only those whose positive terms are ‘infected’ by ill-formed variables.