I looked at velo plugs as part of weight weenie excercise, they may be light but how much!!!????!?
Ive successfully use 25mm squares of cloth based carpet tape to cover spoke holes without any problems. Much lighter and cheaper but takes a bit of time to cut and fit.
Anyway back to topic, presumably this was bad fitting as opposed to rim tape moving?
And if you had disc brakes this wouldnt be an issue.