I generally put on enough dope to seal the covering down - more than a coat. The the tape's a good idea. However, using epoxy, I have not found the amount of dope to be critical, as long as the contact area is rough (porous is better). The only plane I've dismantled so far to save a wing was plenty well attached and took some hefty work to get rid of the fuselage pices around the wing's root. I usually brush on the dope, before attaching the wing; so I don't really have a problem applying less dope to the central strip.
SK