For most supplications I can't see the point of a helper spring, a single linear spring with a spec appropriate to your requirements should be fine, I have some TA coilovers on order myself and the first thing I’ll do is workout the spec’s of the springs supplied eg spring rate and free length, then I’ll try to work out what I actually need and if necessary I’ll buy replacements.
http://www.rallydesign.co.uk/index.php?cPath=1153_1154
Rally Designs (see link) have a large range of springs and at around £15 each (+vat) it will probably be cheaper to replace the main spring than buy helpers.
http://www.rallydesign.co.uk/index.php?cPath=1153_1154
Rally Designs (see link) have a large range of springs and at around £15 each (+vat) it will probably be cheaper to replace the main spring than buy helpers.