I noticed that one of my LCA boots was cracking. I experimented a year ago with the product pictured below. Its intended to repair neoprene, rubber and the like (waders for instance). I bought it at Dicks. It is very flexible when cured. I gave it a shot. I cleaned the boot well, and "scuffed it" prior to application. The "glue" self flattened to the boot. The glossier material on the boot is the product cured. The crack is visible through it, at about the "5 o'clock" position. As the LCA is under tension, the tie down held it down to allow me access. Probably not a forever fix, but working for now, after a year, thought I would share.