I'm running out of wood flour. I'm unlikely to have enough to fillet and tape the inside shear seam. I've already done it in the center of the boat, but am waiting to cut the hatches to complete the seams in the two ends. Do I need wood flour for this, or can I use micro balloons? I was thinking of getting micro balloons for the end pours and wonder if it can do double duty. Or doesn't it have the bond strength needed for a shear seam fillet?