I like the "Hammer Handle Grip" on my fly rods. I made a recent purchase of some rods and decided to modify the grips to my liking. Of course, filling down the flats on the cork exposed all the imperfections. My normal repair was to mix cork fillings and carpenters glue but after a little net research I thought I'd try something different. The recommendation I found was Elmer's Wood Filler, Golden Oak. It cost me $2.98 and it's enough stuff to fill the gaps on all the rods on this forum. Give it a try.
For those of you that have used it, lets hear your thoughts.