The further rearward the more effective they'll be, so as far back as possible on the fuse. You won't notice them if they're on the fuse, immediately below the horiz. stab. The best place, if you can get in there, would be inside the fuse. I prefer to epoxy them or screw them. If using epoxy, wood is a must. If using a screw and 2 sided tape, the covering may not need to be removed.

Do not put them out on the tail feathers, keep them close to the fuse C/L to prevent latteral balance issues. Also, a plane with it's weight towards it's centerline will roll faster and stop rolling faster. Like a figure skater with her arms pulled in to spin faster.

J