TSS - To The Strongest, an ancient set by Simon Miller. An excellent set of rules for large battles using a square grid system marked out on your table top. I contemplated using these (and still might) but went with adapting General D Armee as the lads at the club like them plus they are a good solid rule system. For King and Parliament is a version of TSS for English Civil War and therefore may be easier to change to the WSS period.
Dave.