I just went through this... I converted a mtb frame to ss and used a Forte tensioner kit. The flex from it being a spring tensioner kept throwing my chain alignment off when under load so I took the tensioner apart removed the spring and reinstalled it. Works great for the cost of 25ish bucks. Since it sounds like you are rigged up except for the tensioner all I can advise is to get a springless tensioner (DMR makes a good one I think), use a rigid mount of some sort. Up, down, I dont think it matters but I think up looks best.