'floormuffler' is new to me too. Use the best tape that you can buy, it is part of the vapor barrier. If cheap tape disintegrates in 3-5 yrs., the seams will be open allowing water vapor access to the flooring. When using poly barrier, I also overlap about 6 ins. When using 2-in-1 or 3-in-1 the seams must be butted and your choice of tapes becomes more critical.