Thanks for the info. I found some spec sheets online for the Custom products and compared (they have these at HD). I found that the Flexbond Premium (acrylic included) has the same published strength as Premium Plus with Acrylic Mortar Additive. That seems to support what you learned. The strange thing to me was that the Premium Plus/AMA combination is about 35% more expensive than the Flexbond for the same coverage. It doesn't sound like there's much to gain from the extra $$ if the bags are fresh. I'm also assuming that the products have similar quality since they are the top-line offerings from the same company. Am I missing something?