To be honest selling it is not something I've concerned myself about, I'm building the car for me rather than what someone else might want. I know you should consider all the options but I really wanted something to my tastes.
I bought some permanent fixings for the hard top as the clips were a little "variable" in how well they kept the roof on and I had a lot of wind noise (even over the sound of the straight through exhaust). I bought a set of these which work really well as long as you use the original bolts from the clips.