Hello,I'm an avid F75 user.I mainly hunt old coins & relics in western OH.We hunt old house sites & fields.Our ground is mainly neutral but some field sites are loaded with iron.I've done well with my 3x6 coil.Would there be any advantage with the new 5''DD coil?I normally hunt sens.50,disc.4,3 tones,de mode.I love the sweet high/med tone of a deep Indian head.Also,any preference on frequency?Any input would be appreciated.Much obliged,Mac.