I originally thought spot lock on my Terrova would be too annoying while trying to use my PS21, so I mounted it on a stick that I could turn manually. I actually found it much more annoying to have to constantly have one hand on stick while I was scanning. I put the transducer on the Terrova and now I can keep fishing while using my feet to scan. The spotlock issue doesn't bother me - or hasn't so far, but everyone fishes differently