This is a problem that often pops up when a method of construction that is supposed to make things easier is not done right.... Attempting to sand the indentations away can do one of two things 1) it can make your hull way too thin and/or 2)You will end up with "divots" where the sander concentrated it's wood removal in one area, to remove the gaps, and not in others. This makes for a visually unappealing canoe because of all the waviness in the hull. I don't think that it would affect handling really but the strip thickness I guess is what would concern me. Sometimes gaps such as these are the result of using thicker than 1/4" stock with 1/4" cutters especially on the bead. If this is the case you could "probably" plane the surface even but not knowing specifically what caused the gaps I would be hesitant to suggest sanding all but the smallest gaps out. Doug