It makes perfect sense. I prefer microphones to pickups for acoustic harps, but I have used pickups before and what I did was to use the kind of sticky stuff they use to hold down vases in museums. Living in earthquake country I have most breakable things in my house secured down, so I tried using the same stuff for pickups. What I found works best is not to put what ever adhesive you are using between the pickup and the harp.
Instead put the pickup directly against the wood and then use your adhesive material around the edges or over the whole thing to hold it in place.
I just ran the sticky stuff around the edges and a bit over the top edge of the picup. It worked very well. But I still prefer microphones. They are more hassle but the sound quality is, I find, far superior for acoustic harp.
This is the brand I used, the Quakehold Museum Putty.