should mention that i am not a minelab or coiltek dealer,nor associated with same.assuming your terrain/vegetation similar to sudan/nigeria goldfields,and yor physical condition better than fair,would recomend 18rm,possibly 22rm goldstalkers,with skidplates,one i am considering is the 14x24 em gs,my mts are brushy and steep,ellipticals work well here.bit easier to pinpoint with.cant really speak on the 22rm gs,as never used one,but the 18's are great.couple of tech minded minelabbys (jonothan porter,bruce candy who is the brain behind gpx)have stated that 18 is optimal large coil size.and that larger ones work,but can be prone to saturation.due to the larger magnetic field.so will recomend the 18rm gs,for open country especially.