Now how do you know that its 60mm? did you just compare the FOV with a 60mm lens? or is it the length of the tube? Throw an eye cup on there and your looking pro.
if this is a finder meant for motion picture use, you should probably base it on a s35 image plane, not a 5d. and if you are using a 5d, the 5d itself would make a much better and more accurate finder.
cheezweezl, yes I know, but my canon 5D rig is very heavy, about 5kg total. Only my LOMO anamorphic lens are 2.7kg. So cheap viewfinder would be much better that disassembling rig every time, which is about 15mins.